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General => Douglas Motorcycles - General Discussion => Topic started by: Eric S on 21 Dec 2016 at 22:14

Title: Douglas Aero 1937
Post by: Eric S on 21 Dec 2016 at 22:14
Hello

I just received my Douglas Aero 1937 and I have some questions.
Replies may be on the Forum but it is so rich, I didn't managed to find them yet.

1st about Clutch.
I ususally start on the Neutral between 2 and 3. However when I need to enter the 2 to reach the 1, I have to enter firmly as the gears "crack" and do not enter if going slow.
Clutch cable is adjusted at its maximum with very little free play left on the handle.
Is that normal? Is there anyother adjustment?

2nd about oil
I received the bike with adjustment opened 1/2 turn.
Douglas manual says that 1 1/2 turn is a normal set up.
However at 1/2 turn, oil drips almost continually, I came to 1/4 turn and I have 1 drop / second or more.
I have a lot of oil (I would say too much) making its way to the chain, rear wheel is greasy and when parked, oil drips from the bike's stand.
Bike do not smoke although previous owners says it should smoke when going up hill.

Any help is welcome here.

Thank you for your help or links to post on the Forum.

Eric
Title: Re: Douglas Aero 1937
Post by: Doug on 23 Dec 2016 at 05:02
Eric,

I have a 1936 600 Aero; not on the road but I have ridden one before. A very nice and tractable machine, though not very fast.

Clutch. Like the Velocette clutch, the Douglas flywheel clutch does seem to have a higher chance of being temperamental. For much the same reason, there is little room to spare inside so things need to be in optimal condition.

The best way to check the clutch setting is not at the handlebar, but at the clutch release lever behind the flywheel. With the clutch engaged, this should have the minimal amount of perceptible shake. That will ensure the maximum amount of lift when you pull the clutch lever. As the clutch wears, this gap will decrease, so you need to check the adjustment occasionally. You do not want the clearance to entirely disappear as the thrust bearing will be loaded all of the time and prematurely wear out. The bearing is only used when you lift (disengage) the clutch. Fortunately, the clutch friction material wears very slowly in the Douglas flywheel clutch.

The other issue with the clutch is excessive slop in the components. It is not always wear, as some of it is loose fitting from the factory. The bearings are arranged so they are under the sprocket; more or less. Even so, the chain load tends to tip the clutch plate. A combination of loose fitting parts and minimal lift can allow the periphery of the disk to drag and the clutch does not completely release. Most of this loose fit comes from two locations. The loose roller bearings between the sprocket and the carrier sleeve, and the fit of the carrier sleeve on the hub of the flywheel.

It is difficult to do much with the bearing. The sleeve and sprocket are case hard material. Generally, it is the sprocket bore that is warped slightly out of round. Short of honing and fitting oversized rollers, there is not much that can be done short of a full, engineered replacement of the components. Corrosion and spalling can also take their toll.

A greater source of excess clearance is usually found between the carrier sleeve and the flywheel hub. I have found some of these to be quite loose. As the hub is plated with the rest of the flywheel, I think Douglas left the diameter well undersized so that the sleeve would always fit after plating! This can be a source of problem after re-plating too, as the plating tends to build up a ridge at the end of the hub. I have sorted out this problem by turning the flywheel hub and pressing over it a thin wall bronze sleeve. this also allows the opportunity to lightly hone the inner diameter of the sleeve if it is worn or distorted, and turn the bronze oversized to suit.

Oiling. One drop per second sounds about right; you may find you can cut that back to every few seconds after you get use to it. Do not go by number of turns. Oil viscosity and ambient temperature will many the number of turns mostly meaningless.

Too much oil on the chain sounds like too much crankcase pressure. The oil probably gets dirty very quickly because there is too much combustion gas blowing past the pistons. Could be partial stuck piston rings, or worn rings and cylinder bore. 

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 24 Dec 2016 at 08:20
Thank you Doug for those informations.
I will have to check all this to make sure. However the bike has been supposed to be kind of restoration, flywheel has been re-built...
I am not sure about pistons cylinder and rings but they are also "supposed" to be in good conditions.
As for the oil, is it possible that too much oil from the tap makes this problem without a pressure problem?

Will check that after Christmas,
Thank you for this much usefull help

Merry Christmas
Title: Re: Douglas Aero 1937
Post by: Doug on 24 Dec 2016 at 23:49
Eric,

A flywheel rebuild could be as little as a re-plate and assembly! New linings that are too thick can acerbate the lack of clearances inside the clutch.

The oiling system is a three chamber oscillating/reciprocating pump. Very similar if not identical to the A31/A32 model, so you might want to review this post: http://www.douglasmotorcycles.net/index.php?topic=4288.msg15399#msg15399 (http://www.douglasmotorcycles.net/index.php?topic=4288.msg15399#msg15399)

The full supply of the tap goes to the first stage of the oil pump, that pumps to the sight glass. Any oil that the sight glass does not pass (via the needle valve) just returns to the inlet side of the pump via a bypass.

The second stage of the pump evacuates the sight glass bowl and delivers the oil to the spray bar (over the crankshaft). It you have a leaky tap on the oil tank, you might see the sight glass fill up over time if the pump body is very worn. Granted, this would probably in turn leak into the engine past the second stage eventually if the bike stood at rest for a long period of time. I would think if that were the case you would notice a very smokey engine on startup that eventually would clear as the engine burned off the oil and the pump scavenged the excess back to the oil tank.

Scavenge is the third stage of the pump. There is a weir in the timing chest that sets the correct oil level for the timing gears. Any excess goes over the weir and enters the scavenge inlet of the pump.

Oil to the primary chain on the Aero is vented via a pipe from the top of the front tappet chest. Oil mist in the crankcase migrates to the timing chest on the way to the vent. After establishing the oil level as mentioned and excess being scavenged, any residual mist exits via drillings to the tappet chests to oil the valve stems. There are additional drilling lower down to drain coalesced oil back to the timing chest. There is a natural draught to the front chest, as that has the vent to the primary chain.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 07 Jan 2017 at 10:48
Doug

I am trying to understand the clutch system and having no access to local knowledge, I have to figure out by myself.

The question I have is about adjustment, or how can I check if the clutch is properly adjusted.
When bike is on its stand, idling, on neutral, the rear wheel turns slowly. Seems normal.
When gear engaged and clutch disengaged, the wheel turns harder and can not be stopped easily. If resting on its wheels the bike very slowly (and on flat concrete) moves forward.
If rider on the seat and feet on ground, bike do not moves.

Now the gear lever cracks when engaging slowly the 1 and 2 gears at stop and needs to be engaged briskly.
When rolling, from 1st, the 2 engages well.
So my question is to know if I can ride this bike, entering the 1st gear like a man, or the clutch actually needs to be looked after.

Thanks again for your help.
Title: Re: Douglas Aero 1937
Post by: oily bloke on 07 Jan 2017 at 12:20
Looks like classic clutch drag symptoms where the clutch is not fully disengaging. As described above, the problem can be caused by many things. My EW has had similar problems and as the clutch gets hot when in traffic a previously free clutch can expand to cause drag too. I have found that adjusting the cable so the minimum perceptible play is felt on the lift arm behind the clutch should give a free clutch from cold. If not you may have an oval/worn bearing track causing the clutch plate inside the flywheel to tilt. Having the primary chain too tight will make it even worse. Try running the primary chain much looser than you think is appropriate. I also found that the lift arm tracks where they contact the pins on the crankcase were worn so I machined them back slightly to give a smooth even lift. I replaced the pins too as they were worn as well. Some re-lined friction plates have been made too thick and as there is limited space can cause the plate to not disengage as will excess friction/rust dust. I experimented with spring length and strength to make the clutch light but effective. If all of this fails it is likely the bearing track will need some help! Its a case of fiddle or dismantle and measure. Once it is apart it is self explanatory as to how it all works. The drawings can be a bit confusing.
Hope that helps
Andy
Title: Re: Douglas Aero 1937
Post by: Eric S on 07 Jan 2017 at 17:56
Thank you Andy

However, do you think the clutch on my bike, based on what I tried to describe, needs to be adressed?
Is it normal or not that the gears "crack" when engaged on 30s bikes?
Title: Re: Douglas Aero 1937
Post by: oily bloke on 08 Jan 2017 at 07:47
From what you describe I think you need to address the clutch problems.
The bike should not be trying to move whilst stationary and in gear with the clutch disengaged.
It takes a bit of experience getting the revs and timing right when changing gear on hand change bikes and they can grind a bit if you don't get it right.
Title: Re: Douglas Aero 1937
Post by: Eric S on 21 Jan 2017 at 17:51
Hello

Anyone can let me know what this adjustment screw is supposed to adjust and is it normal it do not sits well in place?
Title: Re: Douglas Aero 1937
Post by: Doug on 21 Jan 2017 at 18:29
It is not an adjustment. The chain case bolts up hard against the frame lug. Looks like a little bit of the chain case ear is broken away; it should encompass the bolt hole. Mine just had a plain hex head bolt, not a shoulder bolt.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 21 Jan 2017 at 18:36
Can you send a pictures of yours?
Mine is also a plain hex head bolt.
Title: Re: Douglas Aero 1937
Post by: Doug on 21 Jan 2017 at 20:37
Mine is apart, but I know I took a photo of this very detail at the Douglas Cavalcade a few years ago. I finally found it squirreled away on the computer hard drive. It is nothing fancy at all. Perhaps the original nut was curved to match the i.d. of the tube, but I do not recall seeing such in the bits and pieces of the two Aeros that I have.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero-primary/Aero-primary-frame-attachment.JPG)

-Doug


[Update image path.  22Sep17 -Doug]
Title: Re: Douglas Aero 1937
Post by: Eric S on 21 Jan 2017 at 22:01
Thank you for the effort. It is well what I understood from your previous description, I was not sure. I will have a closer look tomorrow and see how/of I can make the 2 parts in close contact.
And how I can have it "repaired".
Title: Re: Douglas Aero 1937
Post by: Eric S on 22 Jan 2017 at 09:18
Well I had a closer look this morning.
The part is a bit greasy but from a quick look, I am not sure that the part is actually broken and looks like it is suposed to be open with bo "ear" and the finish is smooth and do not appear to be broken.

To bring him closer to the frame, it looks like I have to take the engine back, then the gear box to maintain the primary chain tension (which is quite loose to this day, concern expressed by Andy).
Now is the question as why it is mounted this way by previous owners. They may have their reason. So is it better to leave it this way???
Can this set up has any effect on the clutch? I don't think so??

As usual, any input more than welcome.
Title: Re: Douglas Aero 1937
Post by: Doug on 22 Jan 2017 at 17:49
The four examples that I have seen just have a hole.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero-primary/aero-primary-rear-attachment.JPG)

At the front, as you probably have seen, there is a little amount of adjustment possible for the engine.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero-primary/aero-primary-front-lower-attachment.JPG)

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 28 Jan 2017 at 12:21
Hello

I tried to make the chain cover closer to the frame and although I still have adjustment left on the mounts, the part is touching somewhere inside. With the flywheel in place, I can not see what is going on there. So I fear I have to let it where it is for now.

I came across this rod that goes between rear of engine and frame. What is is supposed to do?
Title: Re: Douglas Aero 1937
Post by: Doug on 31 Jan 2017 at 19:55
Eric,

That is the "engine adjusting rod". It pushed the engine forward to adjust the primary chain, and stops the engine from creeping backwards over time.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 02 Feb 2017 at 19:14
Thank you Doug
I managed to figure out what the purpose of this rod was in the meantime.
I actually used it to move the engine forward a bit as the primary chain was quite loose.

I also opened the clutch and cleaned the disc. It was covered with a kind of greasy residue that was sticking.
I will have to test the bike but the feel is better.

Also the stand stop is partially "unwelded" and I have to reweld it over the week end. The stand moves too much forward and both wheels remains on the ground when on the stand?
I hope I can repaint the frame to a good standard after this is done.

Besides this, an electrical problem arose and one of the 2 screws that hold in place the chain cover onto the engine has failed. I will try to find a longer screw and see if I can get to fresh threads...

This bike keeps me busy.


Title: Re: Douglas Aero 1937
Post by: Eric S on 06 Feb 2017 at 21:40
Hello one more time

Several bolts and nuts went off and it appear they were not of the correct thread.
What is the thread standard used on those bikes. Is it metric, US or anything else?

Where can we get replacements and how to repair a thread on the engine block? (Primary Chain cover)
Title: Re: Douglas Aero 1937
Post by: Doug on 07 Feb 2017 at 17:11
Eric,

Most of the threads tapped into alloy are BSW. A lot of the other threads are proprietary Douglas, though by the mid-thirties many of these finer threads had been replaced by BSC. I do not think there will be much BSF found on the Douglases until postwar.

Here is a post covering some of the threads in use by Douglas, though nominally up to 1926.

http://www.douglasmotorcycles.net/index.php?topic=1102.msg3721#msg3721 (http://www.douglasmotorcycles.net/index.php?topic=1102.msg3721#msg3721)

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 08 Feb 2017 at 20:02
The 4 bolts clamping the engine on the frame seems to be 3/8 x 20 tpi so it would mean they are BSF.
I am not sure of the 20 Tpi though. It seems to be just a little bit more, the thread gage do not sit well on it.
We have BSW clamping the gearboxx on the frame and the primary chain cover on the engine block.
Most others I checked are BSC.
Title: Re: Douglas Aero 1937
Post by: Doug on 08 Feb 2017 at 22:56
Eric,

Could be BSF or BSC. BSC had a 26 and a 20tpi series. Probably the bolts have stretched a little. I think it was a chronic problem keeping them tight enough. Between the frame tube collapsing, the clamp stretching, and so on, the owner was left with winding down on the bolt more and more in a fruitless attempt to keep the engine from slipping back.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 10 Feb 2017 at 19:21
Doug

do you mean the engine was slipping back anyway?

Beside this, I am still trying to fix my clutch problem. The clutch do not open enough and the gear cracks and the bike want to roll when clutch lever pressed and gear engaged.
The clutch/flywheel assy has been inspected and nothing seems wrong in the clutch.
The period litterature I got with the bike says that the operating cam should open the discs for about 4mm/3/16". (Although I can not find it now and I can find only that the operating cam should lift to a distance of 3/16" so I might be wrong here)
I am far from that with a mere 1-2mm.
I really think the cable travel not enough or at least the operating cam do not rotate enough. Only 1/3-1/2 of the cams are used.
As there is no way to change the cable travel, I come to think that I may have the wrong op. cam and/or the wrong primary chain cover???

I noticed that there is a potential second position for the cable on the op. Cam's lever and a matching hole in the cover where I slide a screwdriver in the picture below.
Title: Re: Douglas Aero 1937
Post by: Doug on 10 Feb 2017 at 21:02
Eric,

If the engine adjuster rod was left with a gap, it slacked off, or the rod bent upward and allowed a gap; sure the engine would probably work its way backward.

You want to maximize the throw of the clutch cam, so that means maintaining the minimal amount of slack in the cable adjustment. Best means is to allow only a little shake of the clutch cam. This will take the pressure off the clutch throw-out bearing. Don't try to set it at the handlebar or by lifting the cable casing at the primary cover adjuster. Those will leave too much slack.

I have seen the second 'boss' on the cam operating arms on the Aero models. Presumably they wanted the same die to be suitable for either style, though I have never seen an application using the shorter arm. Nor does my primary case have the second hole you point out.

-Doug
Title: Re: Douglas Aero 1937
Post by: Ken Rogers on 12 Feb 2017 at 14:52
Hi to make my clutch operate better I reground the angles on the outer operating plate to a steeper angle .This makes the clutch travel further but slightly heavier to use .Works well now no drag !
Title: Re: Douglas Aero 1937
Post by: polly on 12 Feb 2017 at 19:21
Well I had a closer look this morning.
The part is a bit greasy but from a quick look, I am not sure that the part is actually broken and looks like it is suposed to be open with bo "ear" and the finish is smooth and do not appear to be broken.

To bring him closer to the frame, it looks like I have to take the engine back, then the gear box to maintain the primary chain tension (which is quite loose to this day, concern expressed by Andy).
Now is the question as why it is mounted this way by previous owners. They may have their reason. So is it better to leave it this way???
Can this set up has any effect on the clutch? I don't think so??

the primary chain by virtue of the engine sprocket moving out when the clutch operates, means the chain should have enough slack so it will allow the centre line to change, to tight and clutch will drag

As usual, any input more than welcome.
Title: Re: Douglas Aero 1937
Post by: Eric S on 12 Feb 2017 at 19:32
Ken Rogers

Why do you had to reground the plate to a steeper angle?
Do you also had cracking gears on yours?
Before the alteration by how much did you moved out the clutch. I only have 1-2mm.

This modification has been sugested by a friend but seems a bit difficult to make well and I don't want to do it if the problem comes from elsewhere...

Polly,
I made sure the primary chain was loose enough.
Title: Re: Douglas Aero 1937
Post by: eddie on 12 Feb 2017 at 22:31
Eric,
        Check that the friction plate is not dished or distorted, and make sure it runs true to the bore of the hub - otherwise it will always be dragging against either the flywheel or the pressure plate.
 Regards,
               Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 14 Feb 2017 at 19:36
Eddie

I will check the discs runs true.
Right now I am trying to remove the rear primary chain wheel and I am not sure if it's ready to go.
There is 2 nuts that are still in place and I don't know if they need to be removed first.
Looks like these nuts needs to he hammered unless a special tool exist.
By now I removed the washer that I left for the picture.
Title: Re: Douglas Aero 1937
Post by: Doug on 14 Feb 2017 at 19:48
Eric,

There is just the central nut (which you have removed), and the entire chain wheel and cush-drive hub assemble should pull off of the input shaft taper. There will be two Woodruff type keys on the taper.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 16 Feb 2017 at 20:56
I got it off.
I assume the next wheel on the gear box shaft requires also the same extractor?
What is the most period correct finish on the aluminium parts?
Title: Re: Douglas Aero 1937
Post by: Doug on 17 Feb 2017 at 14:52
Yes. Same general design of nut, tab washer, taper, and two Woodruff keys.

-Doug
Title: Re: Douglas Aero 1937
Post by: eddie on 17 Feb 2017 at 15:02
Eric,
       To remove the final drive sprocket, you will need to have a spacer tube and end plate to go over the inner shaft, so that the pressure is applied to the end of the sleeve gear (not the end of the inner shaft). Pressing direct on the end of the shaft is likely to result in the gearbox case being damaged.

Regards,
               Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 18 Feb 2017 at 12:33
Going deeper and deeper.
I reached the gear box shaft where I have a nice oil leak.
What will I found beneath this, what kind of gasket shall I expect and how is it easy to replace?

Concerning the clutch that do not open enough, I made a picture of the part where the cammed wheel turns. I was wondering if there is any adjustment here where I could move it clockwise to kind of "preload" the system.

I made a set up using a comparator that ran through one of the compression spring hole.
With the clutch/flywheel in place, moving by hand the cammed wheel all the way in and out moved  the disc .138"/3,5mm.
Connecting the cable and using the clutch control on the handle bar, the disc moved out 0.065"/1.5mm. That is the maximum traveling available using the control.
Is that enough? How to improve that?
I checked the "flatness" of the disc. It runs at about .010"/0,25mm.
Title: Re: Douglas Aero 1937
Post by: Eric S on 21 Feb 2017 at 12:39
Hello there

I am blocked with my gear box that leaks. Please see picture just above.
Anybody may let me know where I can have some information about the gasket used there, where to get it, and how to dismantle the internals as I fear that the only way to reach this gasket.
Any help will be much welcome.
Title: Re: Douglas Aero 1937
Post by: Doug on 21 Feb 2017 at 17:30
Eric,

The gland is accessible from the outside of the gearcase.

The outer hardened face washer of the sleeve gear bearing has a conical seat. In this seat recess is a leather (or possibly felt) washer. There is a thin collar of "L' shaped cross section pressing against the face of this, which is in turn pressed upon by a wave or spring washer between the gland and the output sprocket.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero-primary/gearbox-sleeve-gland.jpg)

This illustration is for a 3-speed gearbox, but the 4-speed 'box should be the same design.

-Doug
Title: Re: Douglas Aero 1937
Post by: polly on 22 Feb 2017 at 16:46
the gearbox is filled with castrol spehrol, thats why there is a grease nipple on top!
Title: Re: Douglas Aero 1937
Post by: Eric S on 22 Feb 2017 at 17:25
Thank you Polly

I am still wondering why there is a greaser, and 2 nuts for draining and filling??
However I have a liquid oil running though the shaft as you may see on picture.
Of course if there is supposedly no oil in the box, that would solve my problem.
Title: Re: Douglas Aero 1937
Post by: Doug on 22 Feb 2017 at 17:39
Eric,

The type of lubrication for the Douglas gearbox is a re-occurring query here on the Forum. It is a Thixotropic grease, or in other words, self-leveling grease. You can buy it, but most owners make their own by mixing grease and heavy gear oil. The right consistency is you drag your finger through it, it should self-level in a minute at room temperature.

If you use straight gear oil, it does not stay in the gearbox very long. If you use straight grease, the gears cut a path through it, shove it aside, and eventually starve for lubricant. Also it is too thick and viscous to lubricate the sleeve gear bushing.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 22 Feb 2017 at 19:43
Doug

sorry I have some trouble finding some information on the forum that is way too large for me and have not been too lucky when launching requests.

I checked the box. I have a filler on top,  a drain plug underneath and 2 plugs on the sides.
One is at the same level as the shaft, probably for the level? The other one 45 down. Probably a 2nd draining plug.

Consistency is difficult to appreciate. though. But if leaking, it might be too liquid...
I guess the best would be to drain the existing oil and replace with Castrol Spheerol that Poly recommends. That would eliminate the question.
Title: Re: Douglas Aero 1937
Post by: Eric S on 23 Feb 2017 at 11:05
Polly

Castrol makes several Spheerol.
It can be LCX-222, SY-HT2, EPL-2 or EPLX 200-2??

Doug, would you have an ersatz recipe?
Title: Re: Douglas Aero 1937
Post by: Doug on 23 Feb 2017 at 19:04
Eric,

I thought I had a broad vocabulary, but I had to look up ersatz!   :)

No, I do not. I just mix it up ad-hoc when required. Usually in a disposable plastic drink cup, as only a small amount is generally required to fill a Douglas gearbox. For the grease I use general purpose wheel and chassis bearing grease as there is usually a tub on hand in the workshop. You do not need a grease with lithium, though it probably will not affect the outcome. For the oil, generally 90W gear oil or 600W steam oil, depending on what I have laying about. Avoid oils with Extreme Pressure (EP) additives as those can attack certain types of bronze. Mix oil into the grease well until it starts to go fluid. As I mentioned before, my viscosity test is to drag a finger through the surface and see how long it takes to level out. It should be a full minute for the 'groove' to vanish.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 23 Feb 2017 at 19:50
After all you learned me, I am glad I improved your vocabulary !

I guess I will try your recipe as I can not find the right grease. So I can rock 'n roll this week-end... maybe.
Any idea of the volume needed to fill the box? I am a bit concerned about the way I will be able to "read" the level with such a compound not setting down rapidly.
Title: Re: Douglas Aero 1937
Post by: Doug on 23 Feb 2017 at 20:17
Eric,

You just have to be patient. It is going to be slooooooow to pour in as well!

I have never seen a published capacity for the gearboxes. I guess it is about 1 pint or 0.5L. The lower shaft needs to dip into the lube in order to throw it around inside the gearbox. If you over fill it, the excess will have no trouble finding its way out! 

-Doug
Title: Re: Douglas Aero 1937
Post by: oily bloke on 24 Feb 2017 at 06:48
I use a syringe. A big one and inject it through the top.
Title: Re: Douglas Aero 1937
Post by: Eric S on 25 Feb 2017 at 12:08
Draining the gear box. Grease is way too liquid per Doug's specs. Did not pass the finger test. By Far.
Will add some grease to make it less liquid and put it back, less the volume of grease added and I should not be far from being right.

In the meantime I cleaned the outside. Tried to remove a black paint that appeared to be kind of cement to plug probably a hole in the box or maybe something else removed?
Should I ever have to open the box in the future, I will have repaired with "real" aluminium.

Also I am wondering what might be the function of the plug that has a spring loaded plunger on it??
Title: Re: Douglas Aero 1937
Post by: Eric S on 25 Feb 2017 at 17:50
Well finally it was less easy than expected to get the right feeling of thickness. Adding grease, then oil then grease and a bit more oil.
I ended up with what I thought might be right and put the whole mess back in the box (making the grease more liquid by heating at Bain Marie, hey french can cook, it's genetic), level plug open, waiting for everything to come doooooown and self leveling through the port.
Nothings showing up after a couple of hours.
Too thick now?
Will check back when back from skiing middle of next week...

Thanks again for all your help.
Title: Re: Douglas Aero 1937
Post by: Doug on 25 Feb 2017 at 18:55
Eric,

The plunger is the detent for the shift cam drum.

Unless you are certain you mixed up more grease/oil than came out of the box, you will have lost some while pouring it in as it sticks to the case, gears, and shafts on the way down. Even though it is self-leveling, it still is very viscous and will cling a thick film to surfaces. Stick a bend piece of wire in the level hole to see if the level is sitting just below the port. It will give you an idea how much more needs to go in.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 25 Feb 2017 at 20:03
Castrol's Spheerol gear box grease is available from National Motorcycle Museum
http://www.nationalmotorcyclemuseum.co.uk/product/castrol-spheerol-lepo-500gm/

That is yet another Spheerol, not in their regular line, more in their classic line.

Doug,

I added 3 flush Table Spoon of grease, 1 of Oil, lost probably a maximum of 1/2 to 1 TS in the process so I am certain I mixed upmore than came out of the box.
And still nothing shows up at level port or 10mm below as I can see with a bent piece of wire...
Will check again in a few days.
Title: Re: Douglas Aero 1937
Post by: Eric S on 28 Feb 2017 at 16:44
Well, 2 or 3 days later, grease level remains 10mm below the level plug...
I am wondering if level was too low when I started (and did not checked !) or if it is too viscous and sticks to the upper parts of the box.
And the box is still leaking from the shaft !!
I can see a slight play in the shaft. Don't know if this is normal.

As for the foot rest, is the set up below original, with a long threaded on both sides rod and nuts on each end locking everything in place.
Title: Re: Douglas Aero 1937
Post by: Doug on 28 Feb 2017 at 19:15
Eric,

With the output sprocket off, there will be a small amount of axial (end) play in the output shaft. With the sprocket on, the spring washer against the seal should eliminate any axial play. There should be very little radial play, or wobble. However the roller bearings are not spaced very far apart and much of the alignment is provided by the fit of the input shaft through the sleeve gear busing. If that is worn, the sleeve gear can wobble on the shaft and the roller bearings do not have a wide enough 'stance' to prevent it. The input shaft should have a small amount of axial play at all times and no perceptible radial play. Again, if the sleeve in the output shaft is worn, you will be able to wiggle the shaft up and down. If you can perceive it (0.15mm) it is worn out.

Yes, there is a rod that passes through the footrests with nuts on the outside clamping everything together. It looks like the face of the footrest and the sleeve have been modified. These should have a face serration to allow angular adjustment. Pictures of mine attached. The serrations for the brake pedal side are almost entirely worn down. I made new ones. I re-cut the serrations on the foot peg arms.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/serrated-1.JPG)

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/serrated-2.JPG)

-Doug
Title: Re: Douglas Aero 1937
Post by: Doug on 28 Feb 2017 at 19:18
Actually, you may want to ask around about the footrest serration. Perhaps Douglas changed that for the 1937-38 models, because the serrations getting worn and mashed was a chronic problem.   -Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 28 Feb 2017 at 20:38
As for the foot rests, I can see remains of serrations but INSIDE of the right only foot rest. Like if the rod should have matching serrations.
Nothing can be seen on the left.

Any way I will mount it back the way it was. I have more than I can handle for now.
Title: Re: Douglas Aero 1937
Post by: Eric S on 28 Feb 2017 at 20:53
I do have a small amount of axial play on the output shaft. (Providing output shaft is where the Sprocket for Primary Drive mounts or larger shaft)
However I have no "spring washer against the seal". Do you have a picture of that?

Providing input shaft is where the Sprocket for Secondary drive  mounts, or small inside shaft, I have no perceptible play between it and the output shaft.
I am not sure to understand what is the "sleeve in the output shaft" though.
Title: Re: Douglas Aero 1937
Post by: Eric S on 28 Feb 2017 at 21:07
I am not able to identify the thread size of the screws holding the front brake.
I thought it would be 1/4 26 Tpi BSC but is seems to be just a little bit asmaller and 1/4-26 do not screw there.

The original screws on the bike were Allen socket head screws. Anyone has the information as to the correct head shape on those screws?

Also how can we remove this triangular shape plate. Seems to be locked on the square shaft. Do I have to remove the front wheel?
Title: Re: Douglas Aero 1937
Post by: Doug on 28 Feb 2017 at 22:08
Eric,

The original fasteners would be hex head, Whitworth wrench size across the flats. While Allen head socket cap screws were available for the 1920s onward, Douglas did not use them until postwar.

The triangular plate is some sort of modification. So no telling how it was put together. Attached is the very original (and rusty) front end of my 1936 Aero. Also a picture of just the brake backing plate (sorry about the low resolution). The brake arm passes through a bush in the girder fork blade and plugs into a spline inside the brake. A bolt through the center holds the brake arm and shaft from falling out.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero-f-brake-1.jpg)

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero-f-brake-2.jpg)

Markup of the sleeve gear, labeling the parts. I do not happen to have a picture of the wave washer, but it is of the same design as waver washers still sold today.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/gearbox-sleeve-gland-edit.jpg)

-Doug

Title: Re: Douglas Aero 1937
Post by: Eric S on 01 Mar 2017 at 20:30
I just remind that the front brake has been changed by a previous owner. I guess they installed Triumph parts to make it more efficient.

As for the leather gland, is it something hidden inside?
I guess I still miss parts as I can't see how a wave washer stuck between the rotary sprocket and the fixed gear box would handle the friction. Don't I need a ball bearing or the like?
Also I have 3-4mm between the gear box wall and the sprocket. Isn't it too much for a wave washer?
Title: Re: Douglas Aero 1937
Post by: Eric S on 06 Mar 2017 at 12:43
Hello there
On the front brake, original screws seems to be 26 Tpi and about 1/4 but  I can not screw in a 1/4-26 screw. So what it might be?

Doug that is your "bolt through the center holds the brake arm and shaft from falling out".

Doug again, from what I understood on your previous drawing, I should have a leather gland, a backing washer and a spring or wave washer. If those are 3 loose parts that are taken between the gear box and the sprocket, I am lacking them.
Below is a picture of the shafts out of the gear box. I only have the Sprocket to install there.

I found a round gasket, that comes to be slightly compressed between the box and the sprocket. Is that a decent solution unless anyone can tell me where to get the right parts?

Current spark plugs are NGK BP7EVX. Those are completely worn out. Is this model OK? Bike Works well with it...
Title: Re: Douglas Aero 1937
Post by: cardan on 06 Mar 2017 at 21:06

Hi Eric,
It looks like someone has fitted a "modern" lipped seal to replace the original leather seal. Since it has been leaking, I guess you need to replace it. Try to find a replacement before you try to get this one out because the metal casing is often very thin and will probably be ruined if you take it out from the outside.
A gasket of any kind between the case and the sprocket will not work: it won't seal the shaft and it will probably spin with the sprocket and wear the aluminium case away.
Cheers
Leon
Title: Re: Douglas Aero 1937
Post by: Doug on 06 Mar 2017 at 21:23
Hello Eric,

Remember when I said "if they used the same design as the 3-speed". Well they did, and they did not. I pulled the sprocket off of my 1936 Aero gearbox and the seal is not the same as the 3-speed. The housing has no external access to the seal, as you can see in this picture. The aluminum comes right down to the journal diameter.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero-gearbox/1936-gbox-1.JPG)

Which did not match you photo at all. So I looked at another gearbox, this for a 1932 Greyhound 4-speed. It has a design like the 3-speed and the section illustration that I previously posted.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero-gearbox/1932-gbox-1.JPG)

Just to the rear of the keys you can see the spring washer. The spring washer and the backing washer behind it are shown below. The leather gland was missing.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero-gearbox/1932-gbox-2.JPG)

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero-gearbox/1932-gbox-3.JPG)

With this style, the back of the sprocket has a more pronounced spigot that projects into the end recess of the gear case and bear against the spring.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero-gearbox/1932-gbox-4.JPG)

The 1936 sprocket only has a slight hub. The 1936 gearbox for the Aero has a P prefix, the 1932 gearbox for the Greyhound has a GB prefix. It looks like you have this earlier style gearbox?

The spring has a cross-section of 0.062 thick by 0.093 radial, 1.531 outer diameter, and a free height of 0.200 (all dimensions in inches). The backing washer is formed by rolling a lip. The material is 0.036 thick with a inner flange rolled up to make a overall width of 0.088; the outer diameter is 1.739 and the inner diameter is 1.293 (inches). The lip faces outward, towards the spring.

-Doug
Title: Re: Douglas Aero 1937
Post by: Doug on 06 Mar 2017 at 21:27
Eric,

The bolt that secures the brake lever is 1/4-25, a Douglas proprietary thread. They also used 17/64-25 (like for the petrol tank mounting bolts), so you have to be careful.

Picture of the brake arm and bolt in this post:
http://www.douglasmotorcycles.net/index.php?topic=2440.msg8835#msg8835

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 10 Mar 2017 at 20:45
Leon

thank you for your expertise.
The round gasket I'm talking about is a round rubber ring. Being compressed it should pressure the shaft out of the box and limit the leak. Being rubber it should be harmless and help for a while.
I'd prefer to have the box opened, the modified gasket inspected and replaced but can not find anybody locally that may do it. Though waiting replies.

Doug thanks one more time. Don't know what to do. Maybe as just said give this rubber ring a try.

As for the bolts, the "bolt through the center holds the brake arm and shaft from falling out" will be re-installed. I wanted to change as it is an Allen head but will leave it as it is a 1/4-25 and can't find a correct hex head bolt in that size.

I will helicoil the 3 screws on the triangular plate and makes them 1/4-26. The original bolts seems to be also 1/4-25.
Anyway since they were Allen and loctited over worn out threads, I had to discard them + I should be able to live with 1/4-26 there.

The drum being a Triumph, is it possible Triumph also used 1/4-25 there?

On the tank I had a missing bolt so got 4 new chromed 1/4-26 bolts and they screw in 4 turns before being hard to turn. Are they bottoming out or are they 17/64-25?
Title: Re: Douglas Aero 1937
Post by: Doug on 11 Mar 2017 at 03:42
Eric,

The petrol tank bolts are 17/64-25.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 11 Mar 2017 at 18:10
Doug

I measured the 1/4-25 bolts and they are .232"
Seems a bit small for 1/4"?
Title: Re: Douglas Aero 1937
Post by: cardan on 11 Mar 2017 at 21:08

Since they're Allen heads, they might be M6 (6mm x 1mm pitch - 0.236 - 25.4 tpi)!

Leon
Title: Re: Douglas Aero 1937
Post by: Eric S on 12 Mar 2017 at 20:26
Well done Leon, it's well a 6mm bolt.
This bike seems to be a sample of every thread size available in the world.

I re-installed the gear box, clutch flywheel, ...
With the knowledge I acquired through the forum and reading period manuals, I came up to the conclusion that my clutch problems might be linked to an overloaded clutch counter acting on the cam plate/cable action.
So I thought I would adjust the springs to a minimum.
But I think I have too strong springs in there.
Using 2 springs (instead of 6) and screwing in the adjustment nut just 1 turn, I have the plate out of its location but the clutch seems to function and I can turn the primary chain sprocket by hand without turning the engine (so Clutch is well off)
Screwing more prevent that and turning the sprocket turns the engine.
I did not started the engine yet and did not tried "live" but I am really wondering if the sprins are OK.

They are 40mm/1.57" and wire is 0.80"/2mm

Title: Re: Douglas Aero 1937
Post by: Eric S on 13 Mar 2017 at 22:54
Looks like the tank bolts has been helicoiled that would explain the 1/4-26 Tpi bolts fits.

I also noticed the engine bolts fits into inserts that I do not have on the gear box where bolt screw into aluminium. But the inserts are the correct thread size.
Title: Re: Douglas Aero 1937
Post by: Eric S on 15 Mar 2017 at 20:21
Does anybody have any idea regarding the clutch springs discussed just above?
Are they too strong?
Title: Re: Douglas Aero 1937
Post by: Doug on 15 Mar 2017 at 23:34
Eric,

I don't know that anyone bothers to measure them. New ones are available to LDMCC member via the spares department.

As for the engine and gearbox mount. The engine is supposed to have the steel inserts, the gearbox was tapped directly into the aluminum.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 16 Mar 2017 at 11:01
Thanks Doug
I will check with the club.

I noticed a play on the rear wheel sprocket. Do I have a torque converter here?
Title: Re: Douglas Aero 1937
Post by: Chris on 16 Mar 2017 at 11:03
HI Eric
   I have just measured six clutch springs purchased at different times over the years from LDMCC spares. No two are identical. These are a fairly fast moving item and have been purchased from different sources probably on the basis of samples supplied as patterns. The lengths vary between 35.68 and 37.35mm, appreciably shorter than your springs of 40mm. Diameter of coils vary between 12.64 and 13.19mm. The wire diameter also varies between 2.01 and 2.12mm. The subject of clutch springs has been discussed previously on the Forum as other members have experienced difficulty with clutch operation. From my experience with four different models with flywheel clutches none of them needed more than four springs to function well even including a 350cc CW with passenger sidecar.
Chris.
Title: Re: Douglas Aero 1937
Post by: Doug on 16 Mar 2017 at 15:10
Eric,

Quote
I noticed a play on the rear wheel sprocket. Do I have a torque converter here?

Do you mean a shock absorber or cush-drive? If so, no, the rear sprocket is supposed to be rigidly mounted to the rear brake drum/hub/wheel. Having said that, it is only pressed on to a knurled portion of the brake drum. There are several key/blocks that transmit the torque.

-Doug

Title: Re: Douglas Aero 1937
Post by: Eric S on 16 Mar 2017 at 17:08
I don't really know what I mean !
But shock absorber or cush-drive seems to be what I had in mind.

 A friend told me that if the large toothed wheel (with the chain on) moves on the drum where it is installed, then it might be a torque converter.

If it is supposed to be rigid, looks like a new field to play with...
Title: Re: Douglas Aero 1937
Post by: Eric S on 02 Apr 2017 at 19:38
I tested the bike with 2 springs (out of 6) on the clutch, tightened just the minimum I could.

Worked fine but gears still cracks and when going up hill on 4th, the clutch slipped so I had to come down to 1st gear. (steep road) and went back home safely. I hadn't a chance to make more tests as I have to another toy to play with for now.
Cracks seems to be manageable though. Will make more tests later.

Now I also have an elecrical problem. The bike's harness is a real mess with blue wires connecting to reds. Ground being any color but never black !

Dess anyone has a wiring harness plan or drawing fopr a 1937 Aero?
Title: Re: Douglas Aero 1937
Post by: Eric S on 11 Apr 2017 at 12:05
I am sorry that nobody can help with a wiring diagram for my bike.
I can not find a regulator before the dynamo. Are we suppose to get one?
I do a have a diode leaving the amperemeter. Is this replacing the regulator?
Title: Re: Douglas Aero 1937
Post by: eddie on 11 Apr 2017 at 12:43
Eric,
        I don't have any first hand information regarding the wiring on an Aero, but I would assume that it is much the same as that on a 1930 S6 as both machines are fitted with 'Pancake' generators. The S6 has a single wire from the generator to a cutout that prevents battery voltage draining back through the generator windings at low engine speeds. The other side of the cutout is wired directly to the ammeter, and then linked to the lighting switch input terminal. The other side of the ammeter is wired to the live side of the battery. The only provision for voltage regulation is via a ballast resistance on the lighting switch.
    As your bike already has a diode fitted, it would appear that the original cutout has already been superceded. If your bike is fitted with an electric horn, it should be wired directly to the live side of the battery - not through the ammeter!
  Hope this is of some help,
   Regards,
                Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 11 Apr 2017 at 13:11
Thank you so much Eddie
Yes the bike as an electric horn and is wired directly from the battery.
I am forwarding the rest to my helper as I am not able to grasp all the details here.
Title: Re: Douglas Aero 1937
Post by: Doug on 11 Apr 2017 at 15:47
Eric,

I have not yet seen a handbook published for the Aero models, just parts lists. So neither have I seen a wiring diagram. It would have to worked out from contemporary systems.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 12 Apr 2017 at 06:49
Thank you Doug.The bike has been well modified so I am even wondering if a wiring diagram would really help.

Eddie, can you explain briefly the reason why the horn must not go through the ammeter for my personal education?

As for the ballast, I have no idea the way it looks. What I am looking for here?

On the ammeter, I have on one side a direct wire from the + on the battery, and the diode going down (to the dynamo but did not checked it). On the other side of the ammeter, a wire goes to the lighting switch input terminal.
You showed it slightly different with dynamo and lighting switch on the same side and + on the other side.
Does it makes any importance there?
Title: Re: Douglas Aero 1937
Post by: eddie on 12 Apr 2017 at 08:31
Eric,
       It is normal practice to wire the horn direct to the battery as the ammeter is probably only rated at about 4 amps and the horn's start up load could easily exceed that.
     The ballast may be a ceramic coated resistor or just a coiled bare wire between 2 terminals on the switch.
      The ammeter should have just the battery connected to one side - the generator lead (with the diode) and the connection to the lighting switch go to the other side of the ammeter. Wired this way, the ammeter will read the current either going to the battery (charge), or being drawn from it (discharge) - thus giving a continuous reading of whether you have enough charge going to the battery (very important on the Aero as those pancake dynamos often didn't keep up with the drain of a headlight bulb!). One of our local Club members had a 600 Aero that had a reputation for going well, and would often be seen disappearing into the distance - until nightfall - then his battery would go flat within about 15 miles - at which point, he would have to rely on following someone else's taillight!
   Regards,
               Eddie.
Title: Re: Douglas Aero 1937
Post by: Doug on 12 Apr 2017 at 18:50
This is all that remains of my Aero wiring harness. with the exception of the headlamp dip lead, it had been cut where the main bundle left the headlamp shell.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero/1936-switch-1.JPG)

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero/1936-switch-2.JPG)

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/aero/1936-switch-3.JPG)


-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 12 Apr 2017 at 19:44
Is this white curved part with a wire around it a ballast?
Title: Re: Douglas Aero 1937
Post by: Eric S on 14 Apr 2017 at 13:13
I played a little bit and wrote down the harness as it is with colors for the wires.
Beside the diode to dynamo wire that has to be linked to the other side of the ammeter as Eddie required, did any of you see any big mistake or useless connections?
Title: Re: Douglas Aero 1937
Post by: Eric S on 14 Apr 2017 at 13:18
Here is the dynamo, can you let me know where I can plug the earth and the "diode" wire (sorry picture is up side down)?
On the lighting switch, do you see a ballast (picture again not straight) ?
Title: Re: Douglas Aero 1937
Post by: eddie on 14 Apr 2017 at 16:36
Eric,
       As we are looking at the photo of the dynamo (upside down) - the terminal at 4 o'clock is where the diode wire should go. The terminal at 9 o'clock has been added, but is not needed - the dynamo is designed to be earthed via the crankcase and frame.
 Looking at the lighting switch, I am assuming that it is a 3 position switch - that is 'Off - Sidelight - Headlight', and that the switch was photographed in the 'Sidelight' position. If that is the case, your wiring diagram looks to be correct, but with that Lucas switch there is no provision for switching in a ballast resistor. If you have a speedo fitted, the speedo light should be wired to the same terminal (7) as the taillight.
  Bearing in mind that the output from those 'Pancake' dynamos is pretty dismal, you should get away with leaving it permanently connected - it is very unlikely that it will boil the battery dry.
  Regards,
                Eddie.
Title: Re: Douglas Aero 1937
Post by: Doug on 14 Apr 2017 at 18:12
Yes, the white thing is a half-charge resistor.

A ballast resistor is (I think) a resistor used in the specific application of older coil ignition systems with mechanical points.

Here, it is a half charge resistor to prevent over charging of the battery (or accumulator in English). Which is a bit silly, as Eddie says, the output of the BTH pancake dyno is so feeble that overcharging is farce. I suppose back in the day if you ran all day and every day with little night time running the lack of headlamp load could over charge and boil the battery dry. But these days the systems are under-performing (if even working!), the usage is occasional, and often the headlamp on during the day as a daytime running light.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 14 Apr 2017 at 22:25
Eddie

I have an earth wire linked to the 9 o'clock terminal. Should I remove this wire or leave it plugged?
Yes its a 3 positions switch and it's well set on sidelight on the picture. And it has no speedo.
When you said I "should get away with leaving it permanently connected", do you mean that I can leave it permanently connected? Or stay away to leaving it ...?

Do I understand well that the ballast (or half charge resistor) should regulate the voltage so as not to overcharge the battery?
When I bought the bike I've been told that the battery charging by the dynamo was very low so, as Doug pointed, overcharging is not a problem !

I tested the dynamo and I read an 8V output when accelerating the engine a little bit. Sounds to be not too bad but is it relevant or should we check Amps?
How can I check, when everything will be connected and battery installed, that the battery charges beside reading he ammeter. How can I get a value on my meter?
Somebody tested the battery with engine running, connecting on the battery connections and said it was "not charging"?

And is the way the ammeter is wired now, is it possible that the ammeter gives false or no reading?
Title: Re: Douglas Aero 1937
Post by: eddie on 15 Apr 2017 at 12:11
Eric,
         As I have already said, an earth wire from the generator is not necessary as the unit is earthed through the crankcase to the frame.
   Originally, the Aero models were fitted with a Miller lighting switch that was designed to have a ballast resistor (half charge resistor) incorporated in the wiring. Turning the switch to the headlight position would also bypass that resistor so that the full charge rate went to the battery - your Lucas switch does not have that facility, so I would suggest that you should connect the generator via the diode to the ammeter. Connect it to the opposite side of the ammeter to the battery - then any power coming or going from the battery will register on the ammeter. The way it was wired (with the battery and generator on the same side of the ammeter) meant that any charge going to the battery didn't have to go through the ammeter, so the ammeter wasn't reading it.
  When you have everything wired up as I suggested, you can run the engine and see on the ammeter how much charge is going to the battery with the lights off. If it is in the region of 2 - 3 amps, the battery should cope with that. If it is more than 3 amps, you may need to insert a ballast resistor in the generator wire - in order to then get the full charge rate with headlight on, you just need a simple on-off switch wired across the resistor so that you can bypass the resistor when you have the headlight on (thus replicating what the Miller switch did).

  Regards,
               Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 15 Apr 2017 at 18:45
Eddie

I well understood that this wire was useless but it is here. So I will see if it's easier to leave it or remove it.
As I like to understood what I am doing, I came to the  terminal at 9 o'clock and checked it for earth. And it is, as expected. So far so good, it was easy.
I then checked the  terminal at 4 o'clock the one that has the "dioded" wire coming down from the ammeter with +. But this terminal is earthed too. Am I missing something here?
Is it normal due to the nature of the dynamo and the way it works (earth until it comes in production)?
The Diode being supposed to "block" the + going down to the dynamo?
Title: Re: Douglas Aero 1937
Post by: eddie on 15 Apr 2017 at 20:54
Eric,
       The terminal at 9 o'clock is showing a connection to 'earth' because there is a connection through the armature windings. If you were to lift one of the brushes, it would show 'no connection'.

  Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 15 Apr 2017 at 20:58
Eddie

sorry I was talking about the other terminal being on earth. The one at 4 o'clock with + wire with diode.
(Actually both terminals are on earth)
Is that normal?

Eric
Title: Re: Douglas Aero 1937
Post by: eddie on 15 Apr 2017 at 21:08
Sorry Eric,
                Yes, it's the terminal at 4 o'clock that is connected to the armature windings. With a test meter it will show as being connected to earth due to the low resistance of the windings.

  Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 19 Apr 2017 at 16:12
I road tested the bike and although the dynamo seems to output 8V as I measured it some day ago, the ammeter says "0". When lights are on, it goes down to -2,-4.
Is it possible to get an output of 8V but not charging?
For now I am using traditional bulbs. I may change for LEDs to improve battery life but would like to find out if dynamo charging can be fixed.
Title: Re: Douglas Aero 1937
Post by: eddie on 19 Apr 2017 at 18:00
Eric,
       It is possible to have 8V with very little amperage, but very unlikely. If the ammeter is showing '0' going to the battery, but -2, -4 with the lights on, it begs the question "Are the generator and battery wired to opposite sides of the ammeter?"  If not, then the power is not going through the ammeter, so it can't possibly give a reading.
 To check whether the generator is working, disconnect the battery, start the engine with the lights turned on, if they light up then the generator is working.
  Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 19 Apr 2017 at 20:38
Per your previous instructions I wired the + from the battery on one side of the ammeter and the dioded wire (to the dynamo) and the wire to the switch to the other side.
I will test the lights with no battery.
Title: Re: Douglas Aero 1937
Post by: Eric S on 25 Apr 2017 at 10:20
Eddie

I tried running the bike without the battery and the dynamo do not power the lights ! I had not a chance to measure the output out of the dynamo though.

Eric
Title: Re: Douglas Aero 1937
Post by: eddie on 25 Apr 2017 at 11:47
Eric,
       Try running the engine with a bulb connected directly between the terminal at 4 o'clock on the generator and earth - this will establish whether the generator is working. If the bulb doesn't light, there is a fault with the generator. If it does light, do the same with the bulb wired to the other side of the diode and earth - to make sure the diode is wired the right way round!
      If there is no output from the generator, you will need to investigate further - one of our members had a similar problem and that turned out to be a faulty magnet in the generator. I see from the photo of your generator that it is of the later type with a single full circle magnet (earlier models had 2 half round magnets). Now, this magnet should have 4 poles at 90 degree intervals. If you pass a compass around the magnet, it should show the 4 poles equi-spaced - if you get an odd swing of the compass at any other point, there is probably a crack in the magnet at that point - this will cause the generator to internally produce a rogue output that opposes the main output - thus considerably reducing the amperage. Another method is to put a sheet of paper over the end of the generator and sprinkle iron filings on to it - the iron filings will then align to show the magnetic field (just like we used to do in science lessons at school!).

  Hope some of this helps,
                                        Regards,
                                                      Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 27 Apr 2017 at 06:40
Eddie

thank you again for your help. I have been preparing and now leaving for a 2 weeks trip to Morocco (not with the Douglas !) and I will do more testing when I am back.

Best Regards
Title: Re: Douglas Aero 1937
Post by: Eric S on 25 Feb 2018 at 18:25
Well, times flies and only today I decided to work a bit on the Douglas.
I had a ride in the winter and the gears still cracks.
I removed the flywheel and measured the flatness on the clutch using the set up in the enclosed picture (sorry can not make it straight). Well I have only .010"/0,25mm of variation on the disc all around. Not too bad I guess.

I also noticed that I have a black layer looking like burnt grease on the disc. This was present the first time I opened the flywheel and I do not think they are any part of the problem.
ALso the inside of the cone is rather rough. Also not a trouble as I guess as long as the flywheel and clutch disc both truns together, the whole assembly might as well run out of round, it would not affect the clutch.

When I get the bike from Andy Tiernan back in Oct 2016, the gears did not cracked. Report from Andy also says gears goes well and do not crack.
Only after I opened the clutch, cracking appeared. So I am pretty sure I made something wrong when putting everything back together. But assembly is so simple, I can see nothing that might be wrong...

The only adjustment I have are the cable on the primary chain housing. Tightening the cable, preload the cam up to a point the clutch can slip under the kick's action.
And the springs tension plate using the nut on the cam shaft. I tried using 2 springs out of 6, then 3 then very little load.
When I had the bike it had 6 springs and, again, did not cracked.
Maybe I should use 6 springs and load the springs more?
Also I have a very light play on the cam shaft. When taking it with 2 fingers, I can feel (but can't see) a slight play. Not a concern, I guess.
Title: Re: Douglas Aero 1937
Post by: douglas1947 on 26 Feb 2018 at 14:25
Eric,

I had also a problem to engage gears "silent" on my S6, the reason were the 3 rollers on the clutch operating mechanism.
I change the rollers by rollers from a chain (5/8 x 1/4) and get a soft operating clutch.
May be it is worth for a look?

Michael
Title: Re: Douglas Aero 1937
Post by: Eric S on 26 Feb 2018 at 18:29
Do you mean those rollers?
Are they pressed in?
Title: Re: Douglas Aero 1937
Post by: douglas1947 on 26 Feb 2018 at 18:48
Yes Eric,
the studs for these rollers are pressed in.
A change is useful, if the rollers are not round anymore.
On your photo it looks not too bad.

Michael
Title: Re: Douglas Aero 1937
Post by: Eric S on 26 Feb 2018 at 20:27
Yes they look nice. They measure roughly .414"/10,5mm

But I don't think using larger ones for me would help because when I pre load the cable using the adjustment, I can make the clutch slip under the kick. Everything takes me back to a too short cable travel.

Title: Re: Douglas Aero 1937
Post by: douglas1947 on 28 Feb 2018 at 16:15
The size of the rollers is okay (10,3mm).
The ring holding the rollers has several slots to fix it to the pin on the crankcase. Chose the best position for the longest way for the clutch operating arm (to have a long cable travel).
May be it is useful to use a spring to strech the cable?

Michael
Title: Re: Douglas Aero 1937
Post by: Eric S on 28 Feb 2018 at 18:15
Michael

yes there is 3 positions. But only 1 works, the one that makes the cam arm to the lowest position. Using other positions would raise the arm and the cable would be useless.
A spring is on the cable...

Title: Re: Douglas Aero 1937
Post by: Eric S on 05 Mar 2018 at 07:55
I have checked what should have been probably checked earlier, that is the roll bearings and it's not nice.
I noticed that the plate was not turning smoothly and for a cause.
Some of the "square rolls" are well used.
They slightly marked the inside of the "female" part.

The part where the ball bearings are is also marked (even broken) and even though the ball seems to be above the broken lips it may not help at all. Balls do not seem to be damaged though.
I am wondering if we can get larger size bearings so we can re-surface.
Can we get parts from the club? If so I would like to get a link as I don't seem to be able to find where I can go to get those.
Did those parts are heat treated and can be machined?
Anybody ever made new parts?
Title: Re: Douglas Aero 1937
Post by: Eric S on 08 Mar 2018 at 18:44
So nobody ever manufactured such parts?
I received an offer from a member for the bearings.
Before I can get them I need to know how we can "repair" the part or get it.

I see that I need to be a member of the Club to get parts from them. Anybody (club member) can tell me for now if these parts are available as I don't really planned to become a member for now...
Especially if they are not available from them.
Title: Re: Douglas Aero 1937
Post by: Doug on 08 Mar 2018 at 19:08
The clutch carrier sleeve is not available new, you have to find a second hand item or make it. I have made the entire flywheel and clutch, but changed the design of the bearing to ease manufacturing based on the tools I had at the time. Basically changed the two narrow groove for the rollers to one wide groove to take 1/8 needle rollers with a cage to keep them square. It was also the carrier sleeve for the thirties OHV models, which don't have the bearing balls; so not exactly the same as yours. It was written up years ago in the LDMCC's new ConRod magazine. Don't seem to have a photo on the computer, back in the film days.

It is also not uncommon to find the bore in the sprocket oval, or marked where the rollers chattered. If making a new carrier sleeve, you can make an adjustment on the diameter so you can lightly hone the sprocket true. This will help eliminate slop in the carrier sleeve bearing that contributes to clutch drag.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 09 Mar 2018 at 09:22
Thank you Doug
I am going to investigate in 3D printing to get a new part made unles I found an amateur that can make a new one for a decent price...
Title: Re: Douglas Aero 1937
Post by: digcot65 on 11 Mar 2018 at 11:51
Morning, was it the 250cc?I was in the middle of buying one from someone in the club who had a friend with one. Unfortunately, I even paid for the courier to collect the bike and the owner died suddenly the night before I was supposed to buy it.Some people said that the 250cc is underpowered, have you found this. Len
Title: Re: Douglas Aero 1937
Post by: Eric S on 12 Mar 2018 at 09:49
Len

Sorry I can't tell about the 250. Mine is a 600cc.
Title: Re: Douglas Aero 1937
Post by: Eric S on 12 Mar 2018 at 20:08
So after some thinking, I am going to use some new 3/16x3/16 Roller bearings as the rest seems to be in good or usable order.
The grooves for the bearings are fine. The other side is marked but I will run with it.
This should tell me if the clutch now disengage well with the clutch not being drawn by the flywheel due to poor rollers.
If it does, it will be fine. Otherwise, it will be a mess as I have no clue where can be the problem.

If the roller bearings are worn out after a while, I will have the "other side" turned out, will install 5x5mm bearings and this should work.

In the meantime as the flywheel is on "average" condition, I would like to have it refinished.
I assume it was originally chromed as it is now. However the central "ring"of the external/visible side is painted.
Was it painted over the chrome? (I can't see how they would be able not to chrome the center of the wheel...


Title: Re: Douglas Aero 1937
Post by: Eric S on 15 Mar 2018 at 13:48
Well finally I will have a modern cage roll installed.
Using original 3/16 bearings on a marked and damaged outer part will leave damaged bearings in a short time.
So I am going to have this installed once for all...
I know it is not pure original system but I guess it made its time and I had no way to save it.

I did not get a reply re. this :
In the meantime as the flywheel is on "average" condition, I would like to have it refinished.
I assume it was originally chromed as it is now. However the central "ring"of the external/visible side is painted.
Was it painted over the chrome? (I can't see how they would be able not to chrome the center of the wheel...
Title: Re: Douglas Aero 1937
Post by: eddie on 15 Mar 2018 at 19:11
The flywheel would have been masked so that only the required areas were open to the plating process (much like you would mask up an item for painting, but using a material that forms an insulator against the electrical charge that is used to deposit the chrome plate).

  Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 15 Mar 2018 at 20:12
Thank you Eddie
That makes sense. I did not know one could mask during plating ...
Title: Re: Douglas Aero 1937
Post by: Eric S on 26 Mar 2018 at 16:27
Hello friends
Finally I am having the clutch repaired with similar but larger (5x5mm) roll bearings. The modern cage was not suitable.

Anyone know the size of those 4 small screws that screws in the flywheel holding the little plate (that bears a notch to prevent the spring plate to turn)?
Seems to be 4mm(?) 25-TPi
Title: Re: Douglas Aero 1937
Post by: Doug on 26 Mar 2018 at 17:49
3/16-27 

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 31 Mar 2018 at 16:03
Thank you Doug
Any idea where to source them? I would like to avoid hours filing to make them look a little bit better.
Title: Re: Douglas Aero 1937
Post by: Doug on 31 Mar 2018 at 16:58
Eric,

Well it is not a standard thread, as you probably realize. Have you checked with LDMCC spares?

I have made batches of other 3/16-27 threaded hardware on the CNC lathe, but not had the occasion to make that particular screw so do not have any in stock. Would be a bit of a challenge to get as close to the head as they did. I have another job in the lathe at the moment; after that I might try some experimentation. Most of this stuff I have been doing in 17-4PH stainless as it is easy to heat treat so that the slots and hexes don't burr over as easy.

-Doug
Title: Re: Douglas Aero 1937
Post by: ManfrerdSt on 31 Mar 2018 at 18:16
Eric,

what is that for a clutch lining?
looks like cork glued on?

Regards
     Manfred

Title: Re: Douglas Aero 1937
Post by: Eric S on 31 Mar 2018 at 19:00
Yes clutch lining is well cork glued in.
Title: Re: Douglas Aero 1937
Post by: Eric S on 31 Mar 2018 at 19:01
Doug
I was pretty sure it was not standard even though "standard" seems to go a long way when you're talking about english screws.
And No I did not checked with LDMCC as I don't know where to go exactly and I don't have an adress for them.

I may save time, finally, straightening them with a file...
Title: Re: Douglas Aero 1937
Post by: Eric S on 09 Apr 2018 at 14:07
I need to open the gear box on my Aero as I need to check why the kick sometimes seems to miss a tooth.
Is there anything special I need to know beofre I open it?
Is there any risk of having everything fell off the gear box without a chance to find the right place for various parts when re-assembling?
Title: Re: Douglas Aero 1937
Post by: Doug on 09 Apr 2018 at 14:32
Some pictures here:

http://www.douglasmotorcycles.net/index.php?topic=5595.msg20286#msg20286 (http://www.douglasmotorcycles.net/index.php?topic=5595.msg20286#msg20286)

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 09 Apr 2018 at 18:00
Wonderful
Thank you one more time Doug
Do we need any gasket to re-assemble or shall we use a paste?
Title: Re: Douglas Aero 1937
Post by: Doug on 09 Apr 2018 at 19:11
Eric,

None of the ones I have taken apart (grand total of four) do I recall having gaskets. Nor does the 1936 Aero parts list mention any. So it looks like goo it is.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 09 Apr 2018 at 20:13
Sorry Doug??
"So it looks like goo it is. "
Title: Re: Douglas Aero 1937
Post by: Doug on 09 Apr 2018 at 22:48
"goo" = paste, gasket cement. silicon sealant, Yamabond, Permatex, etc.
Title: Re: Douglas Aero 1937
Post by: Eric S on 12 Apr 2018 at 18:10
Hello there

I am considering having this dynamo repaired.
Found a gentleman in UK that can do it for about 400
Add to this a repair I want to have made on the gear box to repair an epoxy, black patch that is plugging a hole on the top of the box and another 400.
On top of the repair for the gear box bearings and a mere 280
And a chroming of the flywheel and 110.
I am just wondering about the insanity of the whole affair.
Can I afford it ? Yes.
Does it make sense? I don't think so.

Not asking a question there, just putting some words together to launch a discussion among the pub/bar/tavern attendance...
Title: Re: Douglas Aero 1937
Post by: Eric S on 07 May 2018 at 20:03
Hello

I see on my front wheel that the part below can be adjusted.
I am wondering how tight/loose I want it?

Eric
Title: Re: Douglas Aero 1937
Post by: Doug on 07 May 2018 at 21:34
Eric,

The usual setting for this type of taper roller bearing hub is so that there is the smallest perceptible lateral moment at the wheel rim/tyre.

Since the original taper roller bearings are obsolete and becoming more and more scarce, some of these hubs have been converted to radial ball bearings. Those should not have any pre-load, and ought to be re-engineered to have inner and outer distance sleeve of the same length.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 28 May 2018 at 16:19
I was wondering if this light was correct for my 19367 Aero?
No I don't plan to change it anyway.
Title: Re: Douglas Aero 1937
Post by: Eric S on 28 May 2018 at 16:20
I had my clutch back with the new bearings.
Flywheel is also back from chrome.
Center was painted black before chroming. Is that correct?
Also am I supposed to paint the inside although I don't see the need.
How was finished the back plate?
Title: Re: Douglas Aero 1937
Post by: Doug on 28 May 2018 at 18:19
The original headlamp would be Miller for 1936-38 Aeros. The shell you have looks like the Lucas wartime or postwar type.

The attached picture is the original Miller No. 74ES shell from my 1936 600cc Aero. Presumably they kept the same model for 1937-38. 

(https://www.douglasmotorcycles.net/proxy.php?request=http%3A%2F%2Fwww.douglasmotorcycles.net%2Faa-files%2Fimages%2Fdoug%2F2018%2Fmiller-74es-shell.jpg&hash=46980604cfdbe9eef47fc95bff5be9b4)

Flywheel. Center is painted black after chroming. I don't know if the factory masked the center during plating or not. Paint does not stick very well to chrome plating, but that might not have deterred them. Nowadays, the easiest solution is just to plate the entire flywheel. This avoids the expense of masking off portions, and avoids the accidental splattering of the mask on areas that you do want plated. Then mask off the areas to remain chrome and use a self-etching primer to get the paint to stick to the chrome. Mask and paint is cheaper than mask and plate. You might want to keep the self etching primer just a smidgen in from the radius of the rim, then overlap the black up the radius to the face of the rim. I find that this allows you to glide a razor blade over the chrome and around the rim to feather back the taped edge of the black paint without revealing primer underneath.

(https://www.douglasmotorcycles.net/proxy.php?request=http%3A%2F%2Fwww.douglasmotorcycles.net%2Faa-files%2Fimages%2Fdoug%2F2018%2F1936Aero%2Fflywheel-paint-sketch.jpg&hash=8d4c29f7945494be79eff2e3efd71d9a)

Inside the flywheel was not painted. Usually it has plating on it, but that was just incidental to the plating process as there was no reason to mask it off. Plating on the hub can mess up the fit of the carrier sleeve. Usually these are too loose and can benefit from building up, but the plating tends to be attracted to external corners and the end of the hub becomes larger than the middle. So the sleeve is tight to get on. Sometime the sleeve is mistakenly honed to get it onto the hub, only to find it as a rattle fit when in position.

What I have done is skimmed the hub and pressed on a bronze sleeve. This I turn to be a precise fit to the carrier sleeve. If the carrier sleeve is worn and needs a light hone, it allows the hub to be made oversized to suit. Eliminating any slop in the carrier sleeve and bearing will go a long way to eliminating clutch drag.

The backing plate is painted black. As far as I can tell the screws were a dull nickle plating, a standard rust proofing finish Douglas kept with into the Aero era, even when bigger items were a decorative chromium plating.

-Doug



[sketch added for flywheel painting. -Doug, 28May18]
Title: Re: Douglas Aero 1937
Post by: Eric S on 28 May 2018 at 18:51
Thank you Doug.
Much usefull as usual.
I talked to a painter and he said that Epoxy paint must be used on Chrome. And I have that on stock.
Hopefully I can do all that during this week.
Title: Re: Douglas Aero 1937
Post by: Doug on 28 May 2018 at 23:17
Flywheel painting sketch added to previous post.  -Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 29 May 2018 at 07:00
Thank you Doug for the extra work detailing your explanation. It's perfectly clear now.
Title: Re: Douglas Aero 1937
Post by: Eric S on 29 May 2018 at 19:52
Made a nice masking with tape,using a rasor blade on my lathe to make a round template.
But I learned something today, you canot sand blast, even at a mere 2 bars or chrome may peel off nickel (I guess).
So flywheel is going back to chrome (he will redo it for me for free).

Question about the front brake. The part on mypart is not from Douglas. It is adapted from anter brand.
What color is the "brake" supposed to be? Right now it is bare alminium. Should I paint it black. What were the fashions back in the days?
Title: Re: Douglas Aero 1937
Post by: Doug on 30 May 2018 at 05:16
Drum, backing plate, and lever are black.

Sometimes you see restorations where the backing plates are left bare aluminum and the lever is plated, but period photos through the thirties show all-black was the standard finish.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 30 May 2018 at 17:46
While preparing the flywheel for the new chrome, I thought that I may put in on my lathe to face it and remove some imperfections.
Starting at a low point where the pain may start I moved toward the center but by doing so I was removing more and more material until I stopped ending with a .3mm step.
it looks like the face is tapered with the center on same plane as the rim??

Now I am concerned about flywheel balancing or should I go ahead and remove this step?
Title: Re: Douglas Aero 1937
Post by: Doug on 30 May 2018 at 18:46
Eric,

Some flywheels, like that for the S6, are tapered between the rim and the hub. They start out from a recess of about a 1/32" below the rim surface and feather out to nil at the center where the clutch spring adjuster ring is. However the correct flywheel for the 600 Aero has the recess a constant depth. The rim is not the same level as the center, though. The recess is still a 1/32" below the face of the rim, but the center is 1/32" proud of the rim; so the step at the center of the recess is 1/16". The idea of the taper was to make the flywheel web thicker towards the center to better resist cracking. Later, perhaps they decided the added manufacturing complication of turning a taper was not worth the effort.

Given that your depth of cut increased towards the center, it sounds like you have a slightly earlier flywheel fitted. Function-wise, I think the whole unit is interchangeable. 

I don't turn the recess. The flywheel is too thin as it is. Since it will be painted anyway, any pitting or imperfections in the recess can be taken care of by the paint primer and filler. I have skimmed the rim, as filling pits on surfaces to be electroplated is a lot more difficult.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 30 May 2018 at 20:01
Doug

Well it is too late now and the concern I have (you did not mentiond balance so it should not be an issue?) is that I have a small step just under the chrome plate (held with 3/16-27 screws) and I see no other way than going center down to erase this step. Step measured at .020"
Right now center remains .025" "proud of the rim"

You said it is too thin there so what shall I do?

Also what color for the 3/16-27 screws?
Title: Re: Douglas Aero 1937
Post by: Doug on 31 May 2018 at 04:45
Eric,

"Too thin" as in you don't want to make it any thinner. As you say, not anything that can practically be done about it now.

Does the step extend under the tin ring that traps the washer for the clutch springs? Basically, that is where the recess on the Aero flywheel ends. If so, leave as is. If it goes under the tin ring, well it is going to create a cosmetic gap that is awkward to fill.

Hopefully you had a slight tool nose radius when turning the recess to avoid creating a stress riser? All things being equal, if you had the flywheel running true in the lathe, what you machined off was an equal amount all the  way around and you should not need to re-balance the flywheel. It probably wouldn't hurt to check the balance, to see if it was in balance to begin with.

The tin ring and the plate for the clutch springs are painted black. Or, at least they are for 1936. I have seen others that were plated, but not sure if some models used a plated ring (the same part was used from 1930 to 38 on numerous models) or the plating was done post-factory. Only the flanged clutch adjuster nut is definitely plated.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/1936-Aero-flywheel-side.jpg)

The four 3/16-27 round head screws that secure the tin ring is a little tricky. Generally small hardware was nickel plated to give a durable, rust proof finish. I cannot see in period photos four bright dots suggesting they were left plated, but I have not come across any views that are one hundred percent conclusive. But it does look as if they were painted over. On my 1936 Aero, the screws were painted (exception to the general small hardware rule) and generally the finish on the bike as found indicates it was never altered. Whether these were things they changed on 1937-38 models to make an inexpensive model change, I don't know.

-Doug


[fix broken image link. 18Apr19 Doug]
Title: Re: Douglas Aero 1937
Post by: Eric S on 31 May 2018 at 08:03
Well I am going to try to make it nice and I will leave it this way.
Yes the step is right at the screw holes so I will have a small gap underneath the plate. It is barely visible but I like to make things nice (although I am limited by my hand's abilities).
You are right to point out the stress riser, I will make sure the step is well shaped.
The tin ring was chrome on my bike so I had it re-chromed.  I shoul live with it.
As for the screws, I have an hi tech silver "paint". Iw ill use it on the screws head. It will blend better with the chrome plate.
There again I should survive with the wrong color parts !

Doug I am really glad you are available. It makes research much easier, faster and accurate. If only my abaility to work was up to the task, I would be delighted...
Thank you !

Title: Re: Douglas Aero 1937
Post by: Eric S on 05 Aug 2018 at 12:02
Hello
It took me a while to work on my bike. In the meantime I had the flywheel chromed, painted and the rollers in the clutch pate replaced with larger 5mm rollers in an enlarged channel. Now the plates with rollers engages the flywheel quite tight (as it should be per the company that made the work)
I installed everything back in place.

Before
The Rear wheel at neutral on the stand was slightly turning and was easly stopped with 1 finger.
Engaging a gear made the box crack. When riding,engaging other gears was fine.

Now with new rollers.
The rear wheel is still turning but with more force. Engaging a gear is cracking a lot.
When pressing the clutch lever, I can not stop with the sole of my shoe the gear box sprocket and everything is turning at flywheel speed.
No way I can ride it now !

Clutch is disengaging for about 2mm when using the lever.

When flywheel is on the bench, launching the sprocket by hand, it goes 1/4 of a turn.
Why at neutral the gear box turns the wheel with engine running whereas when turning the sprocket by hand, at neutral, with no chain, the wheel do not moves?
Why the gear box at neutral turn the wheel with more force than it had with the old rollers?

Any help is welcome.
I am not yet quite fed up with it but getting close.

Eric
Title: Re: Douglas Aero 1937
Post by: Doug on 06 Aug 2018 at 00:12
Eric,

Sounds like the roller bearing is too tight. Unlike a typical cylindrical roller bearing, not only does it need to allow for free rotary movement, but it has to allow free axial moment as well so that the sleeve can move sideways inside the sprocket and lift the pressure plate. Or to put it another way, so the sprocket (and integral clutch disk) can float along the outside of the rollers. It is a bit of a balancing act, as any additional clearance exacerbates the problem of the clutch plate tipping (under the pull of the chain) and the periphery dragging on the pressure or backing plate. It the bearing does not have to be so loose that it drops through while static; it will be rotating at the time. But it does need to be free enough that it can float along the shaft and find a point midway between the pressure plate and the backing plate where - hopefully - it is not touching either! Velocettes are not the only marque with a fickle clutch... As mentioned the hub sleeve and the sprocket bore can be out of round. This makes it difficult to obtain the right running clearance as by the time you get rid of all the tight spots the bearing is now excessively loose everywhere else. If you have tight spots, or the roller bearing is just fitted too tight in general, you will likely also have a problem where any minute variations will cause the assembly to 'screw' the clutch disk one way or the other. That will keep the clutch disk up against either the pressure plate or the backing plate with a few pounds of force, keeping it from disengaging completely.

Also, remember the hub or carrier sleeve needs to slide along the flywheel hub freely (usually the clutch springs and your grip on the clutch lever provide enough impetus), without contributing any more clearance (allowing the sleeve and the sprocket/clutch disk to tilt) than humanly possible. The total lift of the pressure plate free of the clutch disk is limited. So if the disk or the bearing and sleeve it rides upon were to tilt, the rim of the clutch disk can still be in contact with the driven, rotating parts of the flywheel.

However it does sound from your description like the roller bearing is too tight a fit and when the clutch is released it cannot 'float' and find a happy medium clear and free between the pressure and backing plates. Indeed, the very tightness may be driving it up against one or the other. Especially your description of giving the sprocket a twirl on the bench, and it only going a part turn before encountering resistance. If you turn it the other way, does it immediately free off like the clutch disk is screwing away from contact? Can you (partially disassembled on the bench) spin the sleeve inside the sprocket without it threading itself through the sprocket?

-Doug

[Edit, the Aero clutch is single sided and does not have the pressure plate utilized on the big ohv twins. Since the term pressure plate is referenced in subsequent posts and has caused confusion, it is struck out rather than deleted.  07Aug18 -Doug]
Title: Re: Douglas Aero 1937
Post by: Eric S on 07 Aug 2018 at 18:27
Doug
I guess I can see what you mean, barely (lacking again some terminology)...

I check some clearance;
The total movement of the disk in the Flywheel measured from the spring holes with flywheel on the bench (TOTAL movement) is .130"/3,3mm
The movement of the came ring from the lever/cable is .083"/2,10mm
The movement of the disk installed in the flywheel as installed and pushed by the lever/cable/cam is .080"/2,0mm

Just to make sure that this is enough.

Now the interesting thing.
When installed, no chain, I can run the sprocket with fingers and it turns freely, can make it +/-1 turn with 1 knock of the fingers. (The other day I said it was not really turning but I guess it was dragging against the pressure plate. Anyway today it turns "good")

Now If I install 2 springs with the nut barely 1 turn, the sprocket do not turn anymore when pushed with fingers. And if I turn the flywheel by hand, I can barely stop the sprocket with 1 finger.

The only think I can see is that the lip of part #13 pushes against pressure plate #6
Any other idea welcome.

Title: Re: Douglas Aero 1937
Post by: Doug on 07 Aug 2018 at 19:16
Eric,

Oops, I owe you an apology as I forgot the Aero clutch does not have the pressure plate like the big, ohv machines did. So my using the term pressure plate probably muddied the waters. I will strike that out in the previous reply.

The main thing, still, is to check that the bearing is not too tight. If without any springs installed the sprocket can be given a twirl with you fingers and it rotates freely and does not drag to a halt after a turn or two, then that sound fine. Once you start installing springs, I would expect the sprocket to start to offer resistance. Unless you pull the clutch lever, then it should again spin freely!

Referring to your illustration for item numbers: In normal operation, the clutch springs [2] press on the flange of the carrier/hub sleeve [13]. This applies pressure via the ball bearings [8] to the clutch plate [6] and forces it against the backing plate [12] to provide drive. The sprocket is along for the ride. Roller bearings [7] stabilize the sprocket and take the chain load. The bearings only come into play when the clutch plate is lifted, and allow the clutch disk and sprocket to rotate independently, and freely one hopes, from the flywheel.

When you operate the clutch lever, it uses the thrust ball race [5] to shove the whole sprocket and clutch assembly [6, 7, 8, 11, 13] sideways against the pressure of the clutch springs. Once the clutch disk is clear of the backing plate, it should be free. In the case of the Aero, there is no pressure plate occupying the void between the clutch disk and the inside face of the flywheel. This was used on the higher power machines to provide more capacity, the clutch disk had friction material on both side. So lacking the pressure plate, one does not have the problem of running out of space the lift the clutch disk. In theory if the lift were enough the back side of the clutch disk (the side not used for providing drive) could rub or drag on the inside of the flywheel. But I don't think one has enough clutch lever travel for that to ever be a problem. Also I would expect an metallic rubbing sound of aluminum on steel.

When you upgraded from 3/16 to 5mm rollers and enlarged the width of the grooves, how precise were the grooves cut?. Since the rollers do not have a cage, they rely on a nice fit in the grooves to keep them square to the race. It is not enough that they are crowded in there to keep them square.

As far as setting the clutch, you want the minimum amount of slack in the clutch cable so that you have maximum lift. I usually check it right where the clutch cable attaches to the clutch operation arm, behind the flywheel. So long as it can be wiggled in rotation just a smidgen, that is enough slack. Don't expect the thrust bearing [5] to ever stop spinning. It is enough to make sure the pressure is off it, having it idle along due to parasitic drag is unavoidable. Since the clearance is set to a minimum, you do have to check it often to make sure wear of the clutch disk has not allowed it to settle down on the thrust bearing and so bear the load; preventing the disk from bearing against the backing plate.

If the bearing balls [8] and their races are o.k., the flange on the carrier sleeve [13] should not come anywhere close to the clutch disk. It should never rub on it, or the grease slinger [11]. If the rivets for the clutch disk have been replaced by bolts or screws, you have to make sure they clear that flange as well.

-Doug

Title: Re: Douglas Aero 1937
Post by: Eric S on 07 Aug 2018 at 20:10
Doug
It's much easier for me with numbers !

Once you start installing springs, I would expect the sprocket to start to offer resistance. Unless you pull the clutch lever, then it should again spin freely!
Not really. When lever pulled, the resistance is less but I can barely turn the disk with  finger.

I had the rollers' groove re-cut by a company that makes bearings; I assume they know what they are doing...

I have to open it to find some marks on the metal... I am becoming rather good at it.
Title: Re: Douglas Aero 1937
Post by: eddie on 07 Aug 2018 at 20:21
Doug,
         Looking at the illustration that Eric posted, it appears that that clutch would never work properly. The release bearing pushes against the face of the sprocket to lift the cork plate away from the pressure plate. That is OK but the thrust is being taken through the sprocket/clutch plate assembly and it's thrust bearing to lift the carrier sleeve against the spring pressure. That will always result in the flywheel/carrier sleeve/ clutch plate wanting to rotate as a unit instead of allowing the plate to spin free. Now, if the carrier sleeve was shortened to be just proud of the face of the sprocket, the release bearing could then have a reduced inside diameter so that it lifted the carrier sleeve, thus leaving the clutch plate free to turn independent of the flywheel.

   Does that make sense??

   Regards,
                 Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 07 Aug 2018 at 21:01
In any case the drawing comes from Douglas owner's manual.
Should you use a smaller diameter #5 bearing then you would push #13 but clutch plate #6 would not be pushed then and remain engaged.
Title: Re: Douglas Aero 1937
Post by: eddie on 07 Aug 2018 at 22:11
No, Eric, exactly the opposite. The drive is obtained by having the springs pushing against the flange of the carrier sleeve which, in turn, pushes via the set of balls and applies pressure to the clutch plate, forcing it against the pressure plate. If the release bearing pushes against the end of the carrier sleeve, the sleeve will be lifted, releasing the pressure and the clutch plate will drift free of the pressure plate.
   In your illustration, the release bearing bears against the face of the sprocket, so when the clutch is lifted, the full spring pressure is being taken by the thrust bearing between the clutch plate and carrier sleeve - this will provide enough drive to make gear engagement almost impossible. You can easily check this out by removing the flywheel and taking away the clutch release - lightly refit the flywheel and just 2 clutch springs. Use a pair of tyre levers to lift the carrier sleeve and see if the clutch plate/sprocket can be turned freely. (don't lift the carrier sleeve too much or you may dislodge some of the balls in the thrust race).

  Eddie.
Title: Re: Douglas Aero 1937
Post by: Doug on 07 Aug 2018 at 22:43
Eddie,

The sprocket and clutch disk are effectively 'pinched' between the release thrust bearing [5] and the other thrust bearing under the clutch disk [8]. The idea being they are enough of an anti-friction bearing that the clutch disk can rotate freely; even under the pressure of the clutch springs. In reality, there is probably enough bearing drag that the sprocket would never entirely become stationary of its own accord. However the friction of the primary chain and the gearbox ought to counteract that and be sufficient. In theory...

There is a problem with pushing directly on the end of the carrier sleeve [13]. While this will unload the pressure of the clutch springs against the clutch disk, it does not physically push the clutch disk away from the backing plate. You would have to wait for the clutch disk to shuffle away and cease contact, in its own good time. It might just continue to drag against the face of the backing plate. Also, you would be separating the ball races for the thrust bearing [8] - perhaps by as much as the clutch lift - until such time the liberated clutch disk wandered over and closed up the gap. If I remember correctly, the races are like the old bicycle bearing type, or like the 2-3/4hp wheel hubs. There is a bit of a taper leading into the curve of the ball track. So as it separated, it would develop radial clearance. That would allow the clutch disk to hop about off center, with only the bearing rollers biased over towards the sprocket to counteract it. So I think the intention was to keep the balls of the thrust bearing [8] at all time in contact with their race.

I have ridden an Aero and an S6 with these single sided cork clutches, and they are capable of working just fine. But it is like the Douglas internal band brake, it only takes a few non-obvious things to turn them into an infernal PITA.

-Doug
Title: Re: Douglas Aero 1937
Post by: eddie on 08 Aug 2018 at 07:23
Doug & Eric,
         As I said previously, "Now if the carrier sleeve was shortened to be just proud of the face of the sprocket" - I was thinking about 10 thou proud - that would mean the release bearing would lift the carrier sleeve just 10 thou, thus reducing the drag by unloading the bearing[8] before lifting the clutch plate away from the pressure plate. Set up that way, the bearing[8] would have a much easier life as it would only be performing under a lesser load when the clutch is half engaged - with the clutch disengaged, it would be running with the 10 thou clearance, and fully engaged it would be under load but effectively 'static'.

  Regards,
               Eddie.
Title: Re: Douglas Aero 1937
Post by: Doug on 08 Aug 2018 at 15:33
Eric,

Ah, I forgot to factor in that ten thou clearance. That would stop the bearing from separating. The race of the thrust bearing would then have to handle the differential between the speed of the carrier sleeve and the clutch disk, but the clutch disk would be unloaded from end pressure by then and the parts would be greasy. The gap would close as the clutch wore and it would gradually return to the factory design.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 08 Aug 2018 at 17:01
Hi everybody
Stupid here

So, as 13 and 6 were moving together no matter what and the fact that the slightest pressure from the springs was locking the sprocket, I thought that a gremlin was hiding in the #8 balls or #7 rollers.
I took off the whole thing, removed the balls and saw nothing wrong.
Counted the rollers and I had 30 on the lower row and 32 on the upper (keep in mind they are larger 5mm rollers). I was positive that I counted them 3x when installing and had the same amount of rollers on both rows.
So checked in the greasy balls, not there. Mystery.
Put 2 more rollers on the lower raw, slide the 2 parts together.
Then had one more rapid look at the balls and then I saw guess what, 1 roller in the balls. And then another one. My 2 MIA rollers were back !
A 2 years old monkey knows that a square do not fit in a circle and square rollers are probably not doing any good in round rollers.

So now I just have to slide the balls in place; Only concern is that I have 32 ORIGINAL balls. There is enough place for one more ball that I don't have; Can I roll with 1 missing?


Doug your point is mechanicaly sound (I guess) but as  the parts I am using seems to be originals, I will rely upon Mr Douglas assumptions that it should work as it is.
I will keep that in mind however should I have to work on that later.
Title: Re: Douglas Aero 1937
Post by: eddie on 08 Aug 2018 at 18:14
Eric,
        Don't fit the extra ball - the general rule for crowded balls or rollers is to fit a full house minus one, so that adjacent balls/rollers are not pressed together.

Doug,
          Clutch wear will not affect the suggested 10 thou clearance as the carrier sleeve and clutch plate will move as a pair - only wear to thrust bearing [8] will affect that clearance.

  Regards,
               Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 08 Aug 2018 at 18:46
Thank you Eddie
In the meantime I reinstalled the whole set-up as anyway I don't had an extra ball.

It works much better.
Originally when on the stand at neutral the rear wheel was slightly turning.
Engaging a gear was cracking.

Now, rear wheel barely moves at neutral on the stand. However engaging gear still cracks. When clutch is released, the primary chain still turns as you expected. Will adjust  the clutch as Doug said and give her a few kilometers to see how it settles...
I don't know if the pressure on the spring is paramount here.
Title: Re: Douglas Aero 1937
Post by: Doug on 08 Aug 2018 at 20:20
Eddie,

Correct again. My brain seems to be firing only on one cylinder today!

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 26 Sep 2018 at 13:05
Hello dear all

I had not a chance to ride the Douglas until today. Clutch still cracks a lot to engage first gear but then during riding it goes through smoothly. I will try again and maybe there is some break-in taking place.
I would like to check the head nuts.
What is the torque on these?
And what torque on gear box and engine on frame?

Also what pressure do you put in your tires. I am using 3.5x19s.

Edit :
Just noticed what may be a problem
When pressing the clutch lever I noticed that the flywheel moves.
I measured it at +.020" at 12o'clock and +0.00 at 6
Then I moved it by hand and I can definitively feel a play in the crankshaft. When moving by hand the flywheel, measured at 9 o'clock , I can get as much as .040" of play.
Is that normal or too much?
Title: Re: Douglas Aero 1937
Post by: Eric S on 27 Sep 2018 at 08:36
Hello

Sorry if I appear like impatient but I plan to attend the Distinguished Gentleman Ride next sunday with 100-150 kms to do but I would like to make sure I can make it so any comment or advice about my previous questions would be greatly appreciated.
Title: Re: Douglas Aero 1937
Post by: Doug on 27 Sep 2018 at 15:40
Eric,

Never seen any torque value published. Generally manufacturers didn't for stuff of the era. You were just expected to have a feel for the bigger the fastener the tighter you could wrench on it! Basically, what you can comfortably accomplish with open and box wrenches. No sockets with breaker bars; no one had them back then.

When you say flywheel movement or play in the crankshaft, do you mean the flywheel moves relative to the crankshaft or the crankshaft moves relative to the crankcase? Either way, the numbers you mention are grounds for 'do not operate until further investigation'. The flywheel has to be rigid on the taper or the taper will be destroyed. Either axial or radial clearance on the drive side bearing is a major problem. Axial is very serious (could be the incorrectly shimmed for end play) and radial is courting a catastrophic failure. End play should be a slight 0.005-0.010" or so; in other word you should not be able to perceive it. There should be no measurable radial play.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 27 Sep 2018 at 16:01
Thank you Doug

Re. Torque, I tend to over tighten the bolts and nuts usually so I was just asking...

I will take down the flywheel this evening to check the play on the crankshaft and make sure from where this play comes.
I did not checked but I did not felt any axial play, only radial (from side to side)

Will come about it later.
Title: Re: Douglas Aero 1937
Post by: Eric S on 27 Sep 2018 at 20:05
Well I have .030" of fore and art (axial) play
.020" side to side
Not very accurate measures taken on the crankshaft top, flywheel removed.
Noticed the shaft seems to be worst than what I remember. Should not induce play but would not help otherwise.
Title: Re: Douglas Aero 1937
Post by: eddie on 27 Sep 2018 at 22:36
Eric,
       To be brutally honest, with a crankshaft taper that bad, I wouldn't attempt to ride the bike anywhere! No matter how tight you get the crankshaft nut, the flywheel will work loose and do even more damage! As it is, the flywheel will not run true, so the clutch will not free properly. With the amount of play you have on the crankshaft, the whole engine needs stripping and rebuilding.
Sorry to be the bearer of bad news, but running the engine will only make matters worse.

    Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 28 Sep 2018 at 07:43
Eddie

I was ready to hear that.
I will take off the engine (and gear box as the quick tends to rattle, probably some teeths missing inside) so will hurry my winter project.
Any adress where I might go for the rebuild?
Or anybody can guide me in that?
I remember that the crankshaft has been worked on from the documents I had with the bike.
Title: Re: Douglas Aero 1937
Post by: Eric S on 04 Oct 2018 at 09:19
When we'll machine the cone on the crankshaft and in the flywheel, how do we make the parts fit together again.
Is it just a matter of taking the flywheel down the cone a bit more or do we need to sleeve the flywheel?
Title: Re: Douglas Aero 1937
Post by: eddie on 04 Oct 2018 at 10:57
Eric,
        From the photos you have posted and the figures you have quoted for crankshaft movement, your engine needs a complete strip down to check where the problems lie.
        From the basic questions you are asking, I get the impression that you don't have the necessary expertise to do the work yourself, so I would advise you to put the work out to someone who specialises in engine rebuilds.
       To bring the engine back to original spec, the flywheel taper and crankshaft taper (and possibly bearing journal) will need building up and re-machining - otherwise the flywheel will go on too far (maybe by 12mm!).
       From the photo of the crankshaft taper, I would guess that someone has already made a half-hearted attempt at a repair - and in actual fact, made the problem worse, because the poor fitting flywheel has broken loose and done considerable damage to the taper. Unless you are a skilled machinist and capable of carrying out precision engineering, do not attempt to repair it yourself!!

     Regards,
                   Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 04 Oct 2018 at 12:58
I feel pretty confident that I can do it myself. I bought a brand new file and I don't see too much trouble in doing that while watching TV.

No, seriously, of course I will not attend to make it myself and I think I can find a local company that will make the hard work.
I guess I can diassemble the engine and maybe put it back together should I do not find an expert that can do it.
I did not knew material can be built-up.
I just hope I won't find parts in need to replacement that need to be built from billet.

You are again right about the work previously done. I will check from home tonight but I remember having seen an Invoice in the file that was crankshaft related...
Title: Re: Douglas Aero 1937
Post by: Jonathan Hewitt on 04 Oct 2018 at 18:15
Best laugh I have had today ,nice one Eric even with that problem.
Jonathan
Title: Re: Douglas Aero 1937
Post by: Eric S on 04 Oct 2018 at 22:28
The engine is now ready to leave the frame.
Only concern is the magneto. Does it needs to be timed with the engine?
Do I have to make some marks to replace it correctly later?

I went through the documents I had with the bike and several pages concern researches the previous owner made (David, owned it from 2015 to 2016)
He was on this forum and printed messages Eddie and Doug sent him.
Apparently he had troubles already with it, had it modified and it has been modified already prior to his ownership.
The previous modification was made in UK for a french owner but no name on the letter, only 2 pages of drawings and this letter.

Will try to sort this out over the week-end.
Title: Re: Douglas Aero 1937
Post by: Eric S on 08 Oct 2018 at 17:07
Well I have sorted out all the documentations that came with the bike.
However some documents are not dated so I am not sure at what time the crankshaft has been worked on and if several modifications has been made or if it was just discussions.

Anyway I will have to remove and open the engine. So this takes me back to my previous question about Magneto. What is the trick to remove it without loosing the timing or if it is just a matter of re-timing (with professionnal help) upon re-assembling...
Title: Re: Douglas Aero 1937
Post by: Doug on 08 Oct 2018 at 17:35
Eric,

There is no way to practically preserve the timing unless you want to do paint dots on the gears or scratch marks. It is just simpler to re-time it when it gets put back together. Given the other issues that have arisen, I would assume the timing needs verifying anyway, so might as well go through the procedure yourself and know it is set correctly. There might well be marks by the teeth for the valve timing already, though unlikely for the mag. But it is not that complicated to time, so I wouldn't worry about making any special marks.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 12 Oct 2018 at 18:03
Engine is now on my bench.
Anybody can take me on a step by step process to reach the crankshaft please?
Is there and caution To have when disassembling like on the valves?
Title: Re: Douglas Aero 1937
Post by: Eric S on 13 Oct 2018 at 19:21
Thanks To the manual I managed to remove 1 cylinder. To get the second one I need an imperial Allen wrench which I did not have here.
I noticed some extra grease near 1 valve?
The brass part near the oil pump is not nice but seems to work.
Piston is scratched but cylinder is nice and rings has been replaced by previous owner.
Now the manuel do not enter further disassembling so I will need help from now.
Title: Re: Douglas Aero 1937
Post by: Doug on 14 Oct 2018 at 03:23
Eric,

Don't know what the grease is about. The tappet chest should be lubricated by oil mist.

Splitting the cases is pretty straight forward. The only thing that needs special mention is to remove the timing pinion before tapping the crankshaft through. It can be a tight fit on the crank and difficult to get behind it to extract. You might need a special gear puller. The crankcase wall is very thin behind it, so you don't want to be prying against it, or using it to strip the gear off the journal. I cannot remember if the key for the pinion will clear the hole through the crankcase wall, so you will need to check that and extract the key, if required. The ball bearings should be just a light tap (with a rawhide mallet) fit in the crankcases. If stuck, a little heat around the bearing bosses should free it up. If the crankshaft slips out of the ball bearings, leaving the bearings in the crankcase, then just leave them there. Unless the bearings need replacing. On the drive side, there should be a bearing slinger between the crankshaft and the bearing. Between the bearing and the crankcase there may be one or more thin shims that set the end float. Again, it depends if the crank slips out of the bearings, or the bearings slip out of the crankcase.

I seem to recall form older posts for this machine that the oil pump drive is slightly different for the 1937-38 machines, vs. my 1936 Aero. For 1936, the worm has a bronze bush and spins on a steel post that is pressed into the timing cover. For 1937-38, the arrangement was the worm was on an axle, and the bush was in the timing cover. Though I am not sure why the bore is offset so much from the original hole in the timing cover. maybe they needed to alter the location, and that was the easiest way to do it.

Cylinder wall oiling is basically the spray tree from the oil pump dribbling oil in the path of the conrods. This is supposed to line up with shallow grooves in the center web that lead the oil in at the sides of the conrods and so to the big end bearings. See arrow in following image:

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/Aero-crank.jpg)

What misses the grooves get splattered about by the crankshaft and thrown on the cylinder walls. So you will want to verify the spray tree is delivering oil, and that the holes are approximately lined up with the grooves in the center web. Because it looks like there is a problem with the pistons not getting enough oil.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 14 Oct 2018 at 13:26
Doug
since the picture I removed A Nut and B part. I guess the Timing Pinion is what I marked as C.

As for the Bearing Slinger and Shims. I don't saw any shim and I have only 1 washer marked E. No idea what is a slinger. SEE NEXT MESSAGE FOR MORE
As for the spray tree, it points above the conrods but I can not see for now where is the center web from your picture??
For now it looks like there is an anormal play at F. The nut might be not tight but I don't have the right wrench with me.
Bearing on Shaft exit seems OK.
Is it an original set up so far? (except oil pump arrangment)
Do you have any tip as how to test the spray tree?
Title: Re: Douglas Aero 1937
Post by: Eric S on 14 Oct 2018 at 17:40
OK I finally went the whole thing.
I did not find anything really wrong in the bearings, plays or whatever except the play on F described before.
Now I found a home made washer which I really do not like and the wall behind it is cracked and out of shape. (do not seems to be really flat)
I met a company in Birmingham last year that can repair this crack. At least I am going to ask him as the wall is only 3mm thick...
Unless it would be better to machine and put a steel insert?
The red arrow shows a slight mark that do not seem to be a crack.
Would you please confirm the valve cams are on the right position as I did not made marks on them and I need to make sure they do not rotated 180. I don't think so but want to make sure.

Any other comment is welcome.
Title: Re: Douglas Aero 1937
Post by: Doug on 14 Oct 2018 at 17:55
Eric,

Yes, "C" is the timing pinion. It will need to be withdrawn, and possibly its key, before removing the crankshaft from the crankcase/bearing. You will probably have to remove the cam spindle support plate "D" and the inlet and the cam wheels to get good access to the pinion. To get the cam wheels off, you will need to remove the tappets for the rear cylinder that are blocking the way.

There is a keeper plate bridging the two tappet guides, which is pretty obvious. The tappet guides are tapered on the outside and usually need a tap with an aluminum drift to pop them loose. The head of the tappet is too big to exit with the tappet guide, so the tappet guide is slid off the tappet. That means the valve adjusters have to be removed. Once the tappet guide is slid out, the tappet can be cocked at an angle and withdrawn to the inside. A bit of a nuisance, but it makes for a commendably compact arrangement.

"E: is the oil slinger i mentioned. It looks like it was in the correct position, between the crankshaft and the drive side ball bearing. The shims (if any) are behind the bearing; between it and the crankcase. They can stay there until you determine if the crankshaft end float needs adjustment.

"F". The connecting rods can have a little end play with out detriment. I don't know what the official amount would be, but in general 0.008 - 0.015 inch is often encountered for roller bearing connecting rods. I would err towards the loose side because the Douglas crankshaft does flex and you do not want the connecting rod getting pinched! This gap can be checked with a feeler gauge. The bolts that hold the whole the three parts of the crankshaft together should be very tight. You do not adjust the clearance by how much you tighten the bolt, the assembly had to be clamped up solidly and rigid. If not, the flex and motion across the connection will eventually work it loose and fracture the crankshaft.

You will want to check the connecting rod bearings while you are at this stage. They should rotate freely in either direction with no tight spots. Axial clearance as already noted. You should not be able to feel any perceptible radial play. This can be done by spanning you thumb across the connecting rod and crankshaft web and applying pressure and trying to feel any relative movement between the two. Don't take the crankshaft apart unless you have to, though it may be require to repair the crankshaft taper.

Spray tree/bar. It looks like the end of your pipe is open; it should not be. The end should be capped with weld and there will be two small holes pointing down at the crankshaft. It is a matter of checking to see if these holes line up with the grooves in the center web that led oil into the connecting rod bearing. A good time to check it is while the crankshaft is still in the crankcase and can be revolved while making observations. I don't think there is enough volume of oil that it jets out of the hole, so there is no point trying to test the system under pressure. It is more like a dribble in the path of the crankshaft. The spray bar is threaded into the pump body and locked by a jam nut. Axial adjustment is by threading it in or out of the pump body in increments of one revolution and locking it in place with the nut.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/spray-bar.jpg)

At some point, you will want to check that you oil pump is working. That can be done applying some oil to the inlet port and turning the pump over by hand. Oil should be transferred to the outlet. The oil circuit has been dealt with in other posts.




Title: Re: Douglas Aero 1937
Post by: Eric S on 14 Oct 2018 at 19:47
Doug

I assume you replied "only" to the first part of my message.
The spray bar is well closed on the end.
The play at F is like if the large bolt is not tight enough.
I don't have any play at the conrods. Well not so much that I felt it but I have to remove the piston to feel it better.
The only "shim" I found is this homemade washer.
Title: Re: Douglas Aero 1937
Post by: Doug on 15 Oct 2018 at 05:04
Eric,

You posted another reply while I was typing the last message, so it did not address the latest developments.

If the bolt for the crankshaft were not done up very tight, or the joint not pulled up hard against the shoulder of the crank pin race, that would be extremely detrimental to the rigidity of the crankshaft.

Typically there should not be a washer behind the crankshaft pinion. Standard design practice would have this pull up directly against a shoulder on the main shaft. However... The spares list does state part number "18022, Washer behind pinion". So it looks like there is indeed supposed to be one there.

The inlet and exhaust cam are the same part number. So it does not matter which position you install it, or which side faces in; other than the generally good practice of returning everything to its original position because the parts have bedded in against each other.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/20181014_181435-edit.jpg)

The cracks at "A" are typically due to levering off the timing pinion by prying against the rear wall of the crankcase. Folk do not realize how thin it is. As long as there are no lose pieces, it is best left alone. Welding will likely make it much worse. Douglas aluminum (or alumininum) has a very poor reputation for welding and is to be avoided if at all possible. It is very porous, and well saturated in oil. This creates unending impurities when welding regardless of the skill of the welder or how modern their equipment. It is never pretty and often cracks alongside the weld. Plus, you have distortion issues caused by welding. All that is needed is enough of a lip to stop the ball bearing from pushing though into the timing chest. Indeed, part of the crankcase wall is already removed to allow oil to breath into the timing chest at the port "B". So these cracks are relatively harmless.

More worrisome is the crack at "C" as this ties the main bearing in to the rest of the crankcase. And I cannot see how it can be anything but a crack as it spans the machined and cast surfaces. It is peculiar, I have to admit, that it does not seem to penetrate through to the inside of the crankcase. The saving grace is that it is above the bearing and not directly in the load path between the bearing and the cylinders. Still, it is a damnable thing. Do you leave it and hope for the best, or gamble with welding and the problems associated with that?

You could bore it out and put in a steel sleeve. The following is just such a repair carried out on a 350cc crankcase.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/A31-crankcase-repair.jpg)

In this case the entire wall was blown through because the timing pinion was not removed first before extracting the crankshaft. This repair does not really tie the bearing housing into the crankcase, but it does help distribute the load. The saving grace is it is only a 350cc, so the load is not as great. Mind you, the 600 Aero probably only makes 12-15hp.

-Doug


Title: Re: Douglas Aero 1937
Post by: Eric S on 15 Oct 2018 at 11:29
Doug

I forgot a shim. I had well one bearing against the crankshaft larger diameter and the face of the bearing. Side opposite flywheel.

As for the inlet/exhasut cam. Depending how you rotate them, their face can be / or \ hence my question.

Re. the repair, Nicolas Hood makes repairs without welding. They have a special process with screwed in parts and remachining. www.castingrepairs.com
But as you said it does not need repair, I will leave it. I will wait Nicolas' reply though.

As for the crack on C, I checked it again and it is definitively not a crack. It is just a surface mark although I can't explain its origin.

I tried to tighten the large crankshaft nut. A socket won't fit so I have to use a flat wrench. However 28mm is too large (being 28,1mm) even if bolt is measured at 28mm and I don't want to force as it is likely to slip and damage the head which is already not nice.
What is the actual size of that bolt?
Title: Re: Douglas Aero 1937
Post by: Doug on 15 Oct 2018 at 14:25
Eric,

The following timing info is for the 600EW, but basically the same engine design as the 600 Aero.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2017/600EW-valve-timing.jpg)

I do not remember what the crank pin bolt size was. Most likely the hex is a Whitworth wrench size. The next size under 28mm is 9/16W, which has a maximum distance across the flats of 1.010 inch. 5/8W is 1.100 inch.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 15 Oct 2018 at 15:57
Doug

Can you educate me with 5/8W (it looks like it is not 5/8") that makes 1.100".
That is 27.94mm so it might well be the one.

Beside
I have hex nut bolts and Allen bolts on the cylinder heads. Which ones are correct, where to get them and what size are they?
Title: Re: Douglas Aero 1937
Post by: Doug on 15 Oct 2018 at 16:58
Eric,

Whitworth wrenches are a peculiar British institution. Not only did Whitworth pioneer a standard for thread sizes and pitch, but also a suitable size hex head for the bolt. I do not know how he came up with these 'optimum' sizes, as they are all odd sizes (not fractional or metric). This all back in the day of wrought iron and coarse threads. So a 5/8 Whitworth wrench would be suitable or a 5/8 bolt (or thread diameter), with the hex head of course being bigger than the bolt shank. Over time, bolts transitioned from iron to steel and material-wise were more homologous; also a fine thread series (BSF) was needed. So British Standards (BS) which took over for Whitworth (now relabeled BSW) reduced the hex height and increased the hex size. The modern, low profile hex head bolt. This lead to a disconnect between a Whitworth wrench, and the bolt head that it would fit. What was formerly a 5/8W wrench now became a 11/16BS wrench. You will find tables for the wrench sizes online.

I am not sure when internal hex head bolts (Allen cap screws) first came into use. Douglas did use them on the post war models, but you will not find any on the prewar bikes. The cylinder head bolts are 5/16-18 Whithworth thread. The dimension across the hex is 0.437 inch, or 7/16. Not a Whitworth wrench size. I don't know why they chose not to use a Whitworth size (0.445 inch).

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 15 Oct 2018 at 20:01
When I started with the Douglas I had to learn the subtles of the British "Standards" and I even wrote a piece on a french forum on the subject but I never heard that Witworth also "standardised" Nuts dimensions !
Title: Re: Douglas Aero 1937
Post by: Eric S on 17 Oct 2018 at 20:15
I removed the pistons. Checked the play on the rods. Nothing wrong here.
I made my own 5/8W wrench and the flywheel side of the shaft can be tightened almost 1 full turn and I did not forced.
So I will have to find a way to make them tight and maybe Loctited?

On the center web, I have a small screw. What is it for?

Next step is to check for plays on the bearings and then go to a machine shop with flywheel and shaft for rebuilding of the cone connection.
I have 1 piston full of carbon on top and the other one only covered on a 1/3. Any meaning here?
I will re-do the paper gaskets. Previous mechanic that did them made a nice and tight fit around round parts (cylinder bases for instance). What is the trick to cut round holes in paper gasket, at the right place?

Pistons are scratched but the cylinders are nice. I guess they are ancient scratches but will check spray tree though.
Title: Re: Douglas Aero 1937
Post by: Eric S on 17 Oct 2018 at 20:26
While the engine is in parts I will make some paint.
Do I have the correct color scheme on the drive train?
Do I have correct gas and oil hoses?
What improvements would you recommend?
How would you "sand blast" the cylinders?
Title: Re: Douglas Aero 1937
Post by: Doug on 17 Oct 2018 at 23:58
Eric,

The slotted screw on the center web of the crankshaft is a plug for an oil gallery. The 1936 Aero engine was derived from the 1935 500cc "Blue Chief" 500cc Douglas. The Blue Chief had a drilled crankshaft and oil pressure feed to the end on the crankshaft on the timing side. I would appear you have a Blue Chief crankshaft in your Aero. If so, the crank does not have the shallow grooves leading to the connecting rod bearings and the spray bar oiling is not going to lubricate the big end bearings correctly.

The tappet chest covers, dynamo, and entire intake manifold were painted black. No bare aluminum. The copper hot air tube for the carburetor is a facsimile of the original, which was chrome plated steel. The end had a small flare. It extended to the top of the cylinder head, not past it.

The oil lines did have a short segment of flexible hose. The original furrels are a little more rounded on the ends than modern ones. The rubber was not black, but a blue-grey color.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/Aero_flex-2.jpg)

This must have been something common at the time, because the handlebar grips exhibit the same blue-grey color. Note the ends where the grip was protected from the elements:

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/grey_grip_2.jpg)

-Doug
Title: Re: Douglas Aero 1937
Post by: Doug on 18 Oct 2018 at 00:43
Eric,

Original 1936 Aero 600 oil lines.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/Aero-oil-lines.jpg)

Somewhere I should have the fuel line, but I cannot lay my hands on it at the moment.

While the following advert dates to 1937, it shows a 600 Aero in the 1936 petrol tank scheme so must be a left over model.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/1937-Aero-Pride-and-Clarke-advert-1.jpg)

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/1937-Aero-Pride-and-Clarke-advert-2.jpg)

Pride & Clarke were advertising the Douglas line as early as April 30th 1936 issue of The Motor Cycle.

-Doug



Title: Re: Douglas Aero 1937
Post by: Eric S on 20 Oct 2018 at 16:28
I went and checked some details.
- The tree is well adjusted. 2 ports are facing right on each edge of the center web.
- Bearings are turning smooth with no play I can feel.
- Same for Conrods. Only a little barely feelable axial play.
- Tested the oil pump. Oil fed through the bottom port went down through the bottom plug. Then I put oil on the top port and turned pump the other way and oil dropped from the tree.
So I guess it's a pass.
- Checked play on the crankshaft :
   - No play on Flywheel bearing
   - LARGE play on the middle bearing like several millimeters
   - When crankshaft is sled through BOTH bearings, absolutley no play I can feel (see picture below)
   - When oil pump end is fitted, no play either of course.

Now some questions.
1. I made pictures of the marks that tappets are making on the valves. Is the pattern normal or does it tell anything?
2. What shall I do with this homemade washer. Should I make a plain washer of the same thickness?
3. How to lock the big nuts on the crankshaft? Loctite is required and is it enough?
4. I have more carbon on top of 1 cylinder than the other one. Any meaning?
5. Can I sand blast cylinders to paint them?
6. What was the finish on the aluminium parts? Polished, blasted, brushed?

Title: Re: Douglas Aero 1937
Post by: Doug on 20 Oct 2018 at 17:41
Eric,

Sounds like the oil pump and the spray tree/bar is o.k. However if the center web of the crank does not have the shallow grooves, the oil is not going to be able to get into the connecting rod bearings as it ought to.

You will need to be more specific about the clearance in the 'middle' bearing. Is the play in the bearing itself, that is between the inner and outer race? Or is the play in the fit between the bearing and the journal of the crankshaft? Either way, it needs more investigation as it sound like something is amiss.

The long timing side shaft, apparent lack of oil grooves on the center web, and mention of a 'middle bearing' (implying there are three) make me think you have a 1935 crankshaft in a 1936 engine. Have a look again at the photo I posted of my 1936 crankshaft. Note the timing side shaft is short. It ends at the nut for the timing pinon.

Also it contains the answer to your question about crank pin bolt retention. There are supposed to be a tab washer under the bolt head.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/Aero-crank-2.jpg)


1. Marks of the heads of the tappet adjuster from the tip of the valve stem. Normal.
2. Make a new washer, but keep the outer diameter smaller than the root of the gear teeth. The spare list does not say how thick the washer should be. So copy what you have, or try to figure out what the optimal thickness would be to bring the face of the pinion flush with the rest of the gear train.
3. See above.
4. Simplest answer is that piston (and rings) were passing more oil than the other. Be it scoring in the cylinder, rings tired, excessive ring gap, ring flutter, or all the many things that lead to excessive amounts of oil getting past. De-coking engines was a fairly regular ritual back in the day. We are rather spoilt by modern engine in comparison with better air filtration, lack of dusty roads, and lower mileage on vintage machinery as to expect never to do need to scrape carbon. Having said that, both pistons should carbon up at about the same rate.
5. Yes.
6. The aluminum seems to have been 'smoothed-off' at the factory. Or at least in the areas where readily accessible; they did no go into every nook and cranny. Nor did they bother on areas not readily visible, such as underneath. I don't think it was polished to a mirror reflection, more of a satin finish. Most likely it was a job given to the apprentices, so the amount and diligence likely varied from motorcycle to motorcycle. As previously mentioned and shown in the adverts, much of the timing side face of the engine was painted black.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 20 Oct 2018 at 19:03
Doug

The center web has well the oil grooves machined.

As for the play in the middle bearing, It looks like the shaft bears on the aluminium frame, look at the marks on the shaft. So that's where it pivots around.
Bearings measured with a caliper at 24.9mm, shaft measured at 25mm. So considering mesuring internals with a caliper is not accurate it is a good fit.
So it should not pivot???

The pictures shows the shaft entering the bearing but not in place yet.
Shaft is much longer than on your picture. However how would the short 1936 shaft would fill the difference in length?

I have not removed the nuts yet but I don't think I have lock washers? Where can I get them?

What are those aluminium cages on your picture?
Title: Re: Douglas Aero 1937
Post by: Doug on 21 Oct 2018 at 03:33
Eric,

The grooves are deeper and narrower than what the factory used. Someone has modified the center web to work with the 1936-38 oiling system and the spray tree. At least the rod bearings will get oil.

Because the 1936-38 engine uses a spray tree, it does not need to introduce the oil via the end of the crankshaft. That is why the shaft does not need to extend all the way to the timing cover. Nor does the 1936-38 crankshaft require internal oil ways. This probably explains the strange, offset bush in the timing cover. It was part of the modification to install the 1935 crankshaft in a 1936 engine.

The crankshaft stops at the engine pinion nut. The nut has a pair of drive dogs for the oil pump worm. The oil pump worn spins freely on a dowel pin pressed into the timing cover, coaxial with the crankshaft, of course. A picture looking into the timing chest and a view of the inside face of the cover.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/600Aero_timming_chest.JPG)

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/3-stage_pump.JPG)

Now having said that, I do recall from a prior post that there was some differences noted between the 1936-37 and 1938 engines. Specifically, the 1938 engine the worn has a key. In my engine, no key is required. So perhaps they did extend the timing shaft back to the timing chest, though I am not sure why they would bother. They had a lot of other engines with the 'short' shaft and they never seem to have been a problem. I have a 1938 spares list, but while I have seen the 1936-37 spares list, I do not have a copy of it.

As I mentioned, typically there is no shims or bearing spacers on the timing side of the crankshaft, but again, perhaps this was a requirement of using a different crankshaft in the crankcases.

You probably will not find tab washers the right size. It is a small bolt diameter with a large hex head; an unusual combination. Most likely you will need to make them.

The aluminum cages in the photo I used are the roller bearing cages for the connecting rods.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 21 Oct 2018 at 20:58
My shaft being supposedly a 1935, it is however not hollow !?
The worm driving the oil pump is on the main crankshaft on top of the timing pinion and locked with a nut. Then the remaining of the shaft goes in this bronze bushing in the timing chest.
Title: Re: Douglas Aero 1937
Post by: Doug on 22 Oct 2018 at 00:41
Eric,

The crankshaft being 1935 was a possibility. However, as mentioned in the last email it is known from the 1938 parts list that there is something different about the oil pump worm compared to the 1936-37 models. Perhaps the crankshaft is different also, and that it is a 1938 crankshaft fitted. Unfortunately, I do not have an example of the 1935 crankshaft or the 1938 to compare to my 1936. Nor have I seen an example of these components so I have to go be indirect observations.

I do know the 1935 crank fed oil in via the end of the crankshaft. But I do not know if this was via a plain bearing in the timing chest or via an oil quill; they used a quill on several other models. It also used a duplex gear pump at the base of the timing chest. Since your crankshaft does not have a hole drilled in the shaft communicating to the throw (not hollow), it would suggest it is not 1935. I know from mine it is not 1936. Though I do not have a copy, I know the 1936-37 models are covered by a single spares list, suggesting the 1936-37 models were the same. I do not know that for 100% certain, since I do not know the contents. They did issue a new spares list for 1938, and I have a copy of that. But without the 1936-37 list, I cannot compare the part numbers to see if the crankshaft part number changed.

My best guess now is they decided to extend the shaft for 1938 to the timing chest for additional support via a bush, but not necessarily to provide a means of supplying oil via internal drilling. Why they did so when they managed without this additional support since the basic design was introduced with the 600EW in 1927 I have no idea. Nor do I know why it would then have a plug in the crankshaft web, suggesting a cross drilling for internal oiling. Until another similar example turns up it is a bit of a mystery as to what year it is or if it is a mixture of parts from different years.

-Doug

Title: Re: Douglas Aero 1937
Post by: Doug on 22 Oct 2018 at 20:18
Addition pictures of the 1936 timing cover for comparison.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/DSC08150.JPG)

And a closer view. Note no provision in the casting for a bush (indicated by arrow), or gutter to collect oil the bearing.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/DSC08151.JPG)

-Doug
Title: Re: Douglas Aero 1937
Post by: Doug on 22 Oct 2018 at 20:40
The 1937 Aero 600

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/1937-Aero-600.jpg)

Curiously, the cylinders appear not to be painted black.

The 1938 Aero 600

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/1938-Aero-600.jpg)

At some point in 1938 they apparently ran out of cast lugs for the saddle springs and substituted a bit of steel tube with the ends flattened! It did the job and was much simpler (and cheaper). I have seen it on a few late Aeros, so not just a one-off.

Back to your engine, Eric, I wonder what the serial number would indicate what year it is?

1935 Blue Chief (probably ruled out by now) would be 5/H***. A crankcase from the similar Endeavour would be 5/J***.
1936 would be 5/L***, 6/L***, or 6/M*** for the 500 and 600cc models. Not sure what the difference between the 6/L and 6/M is.
1937 would be 6/P*** or 6/PM***. Again, do not know the significance of "M".
1938 would be 6/Q***.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 22 Oct 2018 at 21:36
Doug
here are the serial numbers of the bike.

Eric
Title: Re: Douglas Aero 1937
Post by: Doug on 23 Oct 2018 at 02:16
1937 frame, 1936 crankcases, and crankshaft and timing cover??? The mystery continues!

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 23 Oct 2018 at 10:02
Doug

it is confusing what this bike is. Some kind of Frankenstein's bike maybe.
In any case my main concern is to have it back on the road now.

I considered checking with a local company to repair the cone on the flywheel and crankshaft but I did not had a chance to visit them yet.
In the meantime I was wondering if I should check with a UK based company that may be more used to this kind of work. If anybody has an address to share?
Title: Re: Douglas Aero 1937
Post by: Doug on 23 Oct 2018 at 16:58
Eric,

Douglas changed a only a little bit from one year to the next year (most of the time), so there is a lot of parts interchangeability between years.

I was thinking some more on your description of play in the one crankshaft bearing. Douglas typically used a double row self-aligning bearing on the flywheel side.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/SKF_selfaligning.jpg)

It looks like they continued this practice into the Aero models, judging by what I took out of mine. If so, then being able to swivel the crankshaft around prior to it engaging the second ball bearing is normal. While you still can get the double row, self-aligning ball bearings, it is much more durable to use double row, self-aligning roller bearings. Those were not available back in the day, but it is what I use today in my Douglas engines.

I think the theory for using the self aligning bearings was Douglas knew the crankshaft was going to whip about. Rather than try to resist it and perhaps crack the lightly constructed drive side crankcase wall, they allowed the crankshaft some freedom under the assumption it was more likely to spring back!

Welding up of the taper on the ohv Douglas crankshafts has not always been successful. They tend to break where the weld stops. However, the side valve motors produce significantly less power, so it is probably worth trying.

-Doug


[Fix typo. 23oct18. -Doug]
Title: Re: Douglas Aero 1937
Post by: Eric S on 23 Oct 2018 at 18:01
Doug

the plan was to check again this bearing after work so your message arrived right in time.
I used a piece of metal that slide just tight in the bearing and there is well a side play induced within the bearing. Of course it does not move as much as in your illustration and shouldn't you post this note, I would have said I had a problem with the bearing.
When the shaft is in place, it does touch the aluminium frame only when the shaft is pushed from side to side.
Considering the marks I have on the shaft, I would say the shaft does not turn true, the "self-aligning bearing" does his job and the shaft rubs against the aluminium and makes this small shiny mark.
We should be fine there too?!?

As for the tapet chest covers, the parts I have are chromed (should be black) and they are plain steel, like 1/8" thick. Are they the right parts? Gaskets are made of some kind of rubber and are the same size as the cover. Being held in place with just 1 screw, I can not see how a circumference gasket could make it.

Is there a relation between the loose crankshaft and the shattered cone on the flywheel?

Now to summarise the situation

1. I need to make tab washers for the nuts. I will double this with Loctite.
2. Need an adress to adress the flywheel cone or I will go locally
3. Will try to make a new washer to replace this strange washer I have behind the timing pinion. Isn't it an oil slinger there too?
4. Source engine head bolts. The only one I found for now are those below 5./16W -18 Tpi

Title: Re: Douglas Aero 1937
Post by: Jonathan Hewitt on 23 Oct 2018 at 21:13
Good evening all ,I have been watching with interest. How much metal needs putting back on the taper and is the crank material suitable for hard chroming and then grinding. I have had small marine gearbox output shafts done this way ie 1 1/4 " dia   over a length of 3". just a thought
Jonathan
Title: Re: Douglas Aero 1937
Post by: Bob M on 24 Oct 2018 at 04:06
I've also had gear box shafts built up with an electroless nickel process and found it satisfactory. They required I grind the shaft well undersize to the necessary surface finish first and they then built it back up to size using their process with no further work required by me. I was impressed by the precision of the process.
 
I suppose what Jonathan and I are saying Eric is that there are other ways of repairing the crankshaft taper which do not necessarily involve welding. It's worth checking them all out.

Unfortunately I've never yet found a system that doesn't require the firm application of a thick wad of cash to to get a result.
Title: Re: Douglas Aero 1937
Post by: Doug on 24 Oct 2018 at 05:09
Hard chromium electroplate (versus decorative chromium electroplate) has been used on DT crankshaft tapers with poor results by the late Phil Manzano. Eventually the crankshaft broke at the top of the taper where the plating stopped. It is impossible to ask now if the crank had been baked to minimize hydrogen embrittlement resulting from the electroplating process, though I would have though Phil to be aware of that with his engineering background. At the time it was felt to be a combination of a stress riser where the plating stopped, and well as the very low coefficient of friction that the chromium plated surface had. This low surface friction made it impossible to stop the flywheel from 'shimmying' slightly on the taper even though the joint was lapped, and the added shock loading may have contributed to the premature demise of the crankshaft.

But as mentioned before, the power of the 600 Aero is no anything like a tuned DT, so plating (or welding) may well be o.k. But if you do go with plating, make sure the firm doing the job takes steps to minimize hydrogen embrittlement. If they have plated springs and other hightly stressed parts, they probably already know all about it.

-Doug

[fix typo. 25Oct18 -Doug]
Title: Re: Douglas Aero 1937
Post by: Doug on 24 Oct 2018 at 07:20
Eric,

The tappet chest covers are aluminum castings-

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/DSC08153.JPG)

They are flat on the outer face, but there is a raised boss where the bolt passes through. Also, the edges are well radiused. On the inside they are ribbed. Notice also, even though the inner face is recessed, there is some light milling to make sure the head of the tapper adjuster screw does not touch the cover (on the left side).

The original bolt will have a very small Kingswood trademark, unless it has been polished away.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/DSC08154.JPG)

I have an old stock gasket set, but I do not know who the manufacturer is, or how accurate the material thicknesses are. But the gaskets for the tappet chest covers is a thick pasteboard type material, 0.070" thick. The gasket abuts the crankcase on one side, so rotation is not a problem. Yet it could slide downward, but I guess it was expected to stay tight. After a short while, the gasket probably deformed to the edge of the cylinder casting and that helped keep it in place. Perhaps the factory gasket had a horizontal crossbar across the middle with a hole for the bolt that kept the gasket from dropping down and these aftermarket gaskets I have are a cheap replacement?

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/DSC08157.JPG)

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/DSC08158.JPG)

I looked in the 1938 spare list and they do call out an oil slinger for both the flywheel and timing side ball bearings.

The self-aligning bearing is to allow the crank to flex at elevated rpm, but the main journals should run true. The self-aligning properties are not to accommodate a bent crankshaft. If the crankshaft is bent, the rod bearings are going to have a tough time and you will also likely experience piston seizures due to the pistons being crooked in the bores and developing hot spots.

I made new cylinder head bolts for my engine. Actually I made them several times over. The originals were quite rusty, so I decided to make new ones in polished stainless steel some twenty-five years ago when I first got my '36 Aero. The place I just started working at the time had a CNC lathe and specialized in stainless steel parts. So I made some out of 304 grade stainless, as I did not think the original bolts were made out of anything special regarding strenght. When I tightened the bolts, I noticed they never did pull up tight but just kept turning, and turning , and turning... I took the bolt back out and the 5/16-18 Whitworth thread was 5/16-16 pitch where the thread exited the tapped hole! :( I had underestimated the small (and weak) core diameter of the coarse Whitworth thread. Fortunately it did not mess up the thread in the cylinder.  So I made new bolts out of 420 stainless steel and had the fella at work ruin them through the heat treat furnace. Those ended up so hard they were brittle, and the heads popped off one after the other. :( I suppose the fella could have heat treated them to a lower hardness, but he only knew one process for each grade alloy and for 420 it was dead hard all the way through! Finally I made them out of 17-4PH stainless, which can be heat treated without getting too hard and brittle (about 46 HRc). I don't think the original bolts were plated, I would have to search them out and check.

Recently I made some for my F28 (1928 600EW) that are also 5/16-18, but a different shape to the head altogether.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/F28-Douglas-bolts.JPG)

There may be a relation between the loose crankshaft and the torn taper. If the crankshaft is jerking about the flywheel is going to be jarred and that will only encourage it to become loose on the taper. However, a poorly fitted taper is sufficient in itself to work loose and start fretting and scoring the surface. Mind you, a loose crankshaft is a catastrophe just waiting to happen.

-Doug

[Strike out comment about tappet adjuster clearance, see subsequent post. 24Oct18 -Doug]


Title: Re: Douglas Aero 1937
Post by: Doug on 24 Oct 2018 at 10:03
When reinstalling the tappet covers I noticed that the heads of the adjuster screw do not even come close to the joint surface. So why the one tappet cover has a little extra clearance milled on the inner face, have no idea. Previous post edited.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 25 Oct 2018 at 17:59
Using the enclosed set up I measured the crankshaft for trueness.
Results are not exacts due to my ability to measure and the condition of my lathe.
A = .005-.007
B = .009 - .015
C = .009 - .013
D = .005 - .007
E = .005

Is that good enough or not?
I did not applied too much of a pressure to hold the shaft although when I did it I did not paid attention to that...
Title: Re: Douglas Aero 1937
Post by: Doug on 26 Oct 2018 at 05:15
Eric,

It is impossible to say with that setup. You do not know if you are reading run-out of the crankshaft, or run-out of your mounting in the chuck or the tailstock center; or a combination of all the above. Three-jaw chucks are notorious for not being very accurate. You would need to get the chuck and the tailstock ends indicating zero run-out for the values at A through E to be directly meaningful.

If you were able to get each end running true, the typical number often quoted for two-bearing motorcycle crankshafts (usually single-cylinder engines with full dish crankshafts) is no more than 0.002 inch total indicator reading at the bearing journals.

I have not seen a factory value specified for Douglases. They only stated "Return the crankshaft to the Works for service"!
-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 10 Nov 2018 at 20:07
Hello

today saturday 11/10 I went to the Epoqu'auto show in Lyon, close to home.
I met there several companies that could repair the cone on the flywheel/crankshaft.
One young chap seemed to me to be more inclined to make a good work.
He owns a company making general machining and just set up a new company to build pinions and he's a biker.
He suggested (and indicating a company that could do it) to have the parts welded to add material and he would re-machine on top of that.
He talked about a nitrure surface treatment (not sure of english name on that) after machining. Is it a good idea or will this led to fracture points?
He said that the welding company might be able to match the RC of the original part which sounded a good idea.

Do you have (Doug?) the factory dimensions of the parts there. He can measure them with accurate lab style tools but I am a little bit concerned that the condition of my parts may not allow to make accurate measurements or the flywheel might even crawl too much on the shaft.

I will get back to the show tomorrow 11/11 so I can ask him more even though I still can reach him after the show of course...
Title: Re: Douglas Aero 1937
Post by: Doug on 10 Nov 2018 at 23:20
Eric,

This is the specifications for the 1930 S6 crank taper, but I believe it is the same for the Aero.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/crank-taper.jpg)

Dimension in inches. On the flywheel side the diameter at the face is 1.160 inch, a little less than the full journal size of the crankshaft.

Not all metals can be nitrided, so some careful attention tot he weld materiel will be required. The tempering temperature for crankshafts was generally around 760C 600C, so nitriding temperatures of 550-575C for gas nitriding should be safe. The rest of the crankshaft will need to be masked to protect it from nitriding and oxidation.

Probably the greatest risk stress cracking is from the welding itself, rather than the nitride hardening. Nitriding is typically a shallow treatment, nor do you require much depth for the flywheel taper. You just need a hard skin to resist fretting and galling. Since the nitriding adds an additional cost, you may want to investigate welding up the taper with a hard facing material and forgo the nitriding. Stellite or manganese steel are two possibilities.

-Doug

[Correction to tempering temperature. 760C used on OHV crankshafts, 600C used on side-vale crankshafts. 11Nov18 -Doug]
Title: Re: Douglas Aero 1937
Post by: Doug on 11 Nov 2018 at 05:18
Correction: lt looks like some of the side-vale cranks were tempered from 600C. Still above the nitriding temperature.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 12 Nov 2018 at 16:43
While the engine is out of the bike, I will have the dynamo refurbished so it can (maybe) charge the battery.
In 2013, previous owner had an invoice for "BTH M2 CAM RING"
Any idea what this might be.
I have been asked by the re-furbisher if the regulator was inside the dynamo or separate. He needs it so I need to find it but I have no idea what to look for.
Title: Re: Douglas Aero 1937
Post by: Doug on 12 Nov 2018 at 17:27
Eric,

"BTH M2 CAM RING" is a ring in the magneto that operates the points.

The dyno does not have a regulator. Trust me, overcharging is not a hazard with the BTH pancake dyno!  :)  There is a BTH cutout that attached to the frame using the nut that holds the post for the hand change lever. This is what the cutout looks like, but the correct bracket is a triangular affair of flat sheet metal.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/P8040001.JPG)

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/P8040002.JPG)

You can just see the bracket attached to the frame in this picture.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/scan0101a.jpg)

-Doug

Title: Re: Douglas Aero 1937
Post by: Eric S on 12 Nov 2018 at 17:59
I do not have a BTH Cut out. There is nothing screwed on the gear level post.
I do have a diode on the wire from Ameter to Dynamo though.
I guess it's doing the same.
Title: Re: Douglas Aero 1937
Post by: Eric S on 13 Nov 2018 at 18:55
Doug
Do you have enough head bolts that you may want to sell?

I checked the crankshaft bearings and there is several hard spots I dis not noticed before. I Guess new ones are mandatory. How do we remove them?
I may check that with bearing supplier...
Title: Re: Douglas Aero 1937
Post by: Doug on 13 Nov 2018 at 19:46
Eric,

The head bolts that I made are for an earlier model (600EW) and so have a different (and much more ornate) head than what the Aero used. The Aero head bolt looks like this:

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/headbolt.JPG)

A tall hex head, domed, and the thick, plain washer. I don't know that these should be bright; I think originally they were cylinder black. My originals were rusty and quite pitted so I had remade them (many years ago now). I would have to dig the originals out of storage to see if the shanks had any trace of nickel plating on them, but I do not remember such.

The standard practice for getting the crankcase bearings out is to gently heat the surrounding aluminum with a propane torch until just to hot to hold and than thump the crankcase face down on a block of wood so that the inertia of the bearing causes it to drop out of the bore. If it it particularly stuck in place reaching through with a soft drift tapped against the inner race to get it started is o.k. Be sure to work your way around equally so as to not cock and jam the bearing in the bore. Note that hammering on the bearing so that the shock is transmitted through the balls is a definite no-no, but light tapping is probably o.k., and if you are going to replace the bearings anyway it doesn't matter.

-Doug


[fix typo. 31Jul19  -Doug]
Title: Re: Douglas Aero 1937
Post by: Eric S on 13 Nov 2018 at 20:50
I have well the same screws at least on one 1 cylinder. And they are plated.
Allen screws on other cylinder.
I would like to have same screws on both sides even if not originals...

On a different matter,  how do we handle unleaded gas?
Title: Re: Douglas Aero 1937
Post by: Eric S on 14 Nov 2018 at 08:49
What are the tanks capacities?
I will have the tanks treated with a resin and I need to get that information to order the right kit.
The reservoir is well made of steel (not aluminium)?
Title: Re: Douglas Aero 1937
Post by: Doug on 14 Nov 2018 at 14:42
Eric,

3.5 gallons fuel and 3 pints oil.

The lack of leaded fuel is generally not a problem unless you run high mileages or run the engine hard for continuous periods such that exhaust valve seat overheats and starts to transfer metal to the valve (valve seat recession). Leaded fuel, introduced in the thirties, helped combat that.

The increasing use of ethanol in fuel is a more significant issue, and you may find you will have to alter the carburetor settings to compensate. There have been quite a few posts on that topic relating to the postwar models.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 14 Nov 2018 at 15:31
Doug

Thank you for the information. I am assuming that is Imperial gallons and pints even if it do not make a huge difference with US standards.
Any idea about the head bolts? Any spare to spare? Anybody knows where we can get them?
Title: Re: Douglas Aero 1937
Post by: Doug on 14 Nov 2018 at 17:25
Eric,

The tank capacity came from their catalog information, so would indeed be Imperial units vs. US. When in Rome, as the Romans do...

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/1937-Aero-600.jpg)

I did not make any extra of the Aero head bolts at the time (it was 25 years ago),  though these days when I do make something like that I often run off a few extras when I have the machine set up. I do not have any plans to run them again as I have too many other things to machine, but could provide a drawing if you can get them machined locally. Otherwise it would be a matter of advertising here or in the LDMCC magazine.

Unfortunately, and for no good reason I can see, the head bolts are different between the 500/600cc Aero and the 250/350cc Aero.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2018/1936Aero/aero-head-bolts.JPG)

Both 5/16 diameter, but one a fine thread and the other coarse. Also different lengths, height of dome, and even diameter of the washer. They could well have used the same bolt for all four engines, but did not. Which is a pity as quite a few of the 250/350cc engines have been scrapped looking for crankshafts and conrods that can be altered to keep the 350EW running, so someone might have saved some cylinder bolts and other hardware. However they will not do you any good for a 600.

As you can see, no trace of plating, so original finish would have been black stove enamel.

-Doug


Title: Re: Douglas Aero 1937
Post by: Eric S on 22 Nov 2018 at 08:06
Well I found a company that could make the bolts but for just a set they said it would not be effective.
I posted a message in the parts of the forum but nobody interested at this time...
So I will stay with the current set up for now until I found a solution.
Title: Re: Douglas Aero 1937
Post by: Eric S on 28 Nov 2018 at 16:46
I removed the valves to paint the cylinder and heads.
I marked them to put them back on their respective port but is it required to rotate them to the same position? (I marked them to do so anyway)
Also do we have to clean them down to bare metal?
Title: Re: Douglas Aero 1937
Post by: douglas1947 on 28 Nov 2018 at 17:44
Hi Eric,

have you checked the valve seats / valve surfaces?
When you have the valves out, it is a good chance to "fresh up" the seats with regrinding.

Michael
Title: Re: Douglas Aero 1937
Post by: Eric S on 28 Nov 2018 at 19:21
No I did not checked but I will have to show them to somebody with more knowledge and probably regrind...
Title: Re: Douglas Aero 1937
Post by: Eric S on 10 Dec 2018 at 20:15
I finally had a chance to pay a visit to the company I met at a show last month so they can rebuild the flywheel/crankshaft cone.
We may not go to welding as the flywheel can not be welded all the way in and it would be better to use an intermediate cone. He's thinking right now as to what he can do.

It looks like I will have to have the faces of the valve lifters resurfaced as they are slightly marked. I thought it was fine, he said no.
Also a rubber has been placed behind the bearing on the flywheel side. Is that original?
The bearing is marked SRO. This is a french company that went out of business during the war, so I think the bearing might be original. I will keep it as it's good enough.
The other one will be replaced as it was not quite nice although quite usable.

Sandwiched between the SRO bearing and the rubber I have a thin washer. The mechanic said it was useless and he "would not put it back" as he see no use to this.

Any comment will be appreciated.

Cheers
Title: Re: Douglas Aero 1937
Post by: Doug on 11 Dec 2018 at 07:33
Eric,

As mentioned previously, there should be a oil slinger between each end of the crankshaft and the adjacent ball bearing. Not only does this limit the amount of oil blowing through the bearings, it stops any large debris that inadvertently might get loose inside the engine from getting into the bearing. If your mechanic does not recognize an oil slinger and the use thereof, find another mechanic! Between the flywheel side bearing and the crankcase will be any shims required to limit end float of the crankshaft assembly. Even back then 21mm wide double row ball bearings were going out of style, so a 20mm bearing and a 1mm shim was the normal starting point; and then the shims were added to set the end float. I cannot just now remember for certain if there is a felt seal on the drive side; I am reasonably sure it did have one. Often there was on many of the models in this era. If there is a 3/6 to 1/4" deep recess in the crankcase between the bearing and the crankcase wall, then it certainly had a felt. If so, then another oil slinger is required to act as a shield and keep the felt out of the bearing. They were not using rubber rings or seals.

Most late-twenties and thirties Douglas engines that I have taken apart where I felt the bearings might have been original were SKF or Norma-Hoffman brands.

I don't think the face of the tappet adjusters is particularly hard, so resurfacing them and accidentally cutting through the case hardening should not be an issue. The problem with the wear is that you don't know exactly where the valve stem is going to land after a new adjustment. So if it lands half on the original surface and half on a worn pocket, you only have half the full bearing surface. As the valve stem is likely harder than the tappet adjuster, it will rapidly wear into the face of the tappet adjuster until the contact patch approximates the full diameter of the valve stem. Which means the valve clearance will go out of adjustment quicker than it otherwise might have.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 11 Dec 2018 at 09:33
Well I will check with him about the oil slinger; I am surprised as he's definitively involved in motorbike engines and even though a young businessman, he built a lot of motorbike engines, working on hi-performance 2 strokes engines and working earlier for a motorbike restoration company.
The bearing in place now is well a 21mm.

It looks like a least one felt has been replaced with a rubber on this engine... I will check the other end.
Title: Re: Douglas Aero 1937
Post by: Eric S on 11 Feb 2019 at 16:16
---
Title: Re: Douglas Aero 1937
Post by: Eric S on 11 Feb 2019 at 16:18
I still wiat for the repaired crankshaft to come back...
In the meantime I would like to attend a concern with the kick.
When I use it there is a feeling like if teeths were missed on a pinion.
I see return spring has been changed in 2005 and 2012 and in june of 2012, a hand written note says "Kick Start "POB" and in may of 2012 a Spur Gear Standard Bossed has been invoiced by HPC Gears Limited.
Not sure if those last 2 items are related?
What should I check first. Do I need to open the gear box?

Title: Re: Douglas Aero 1937
Post by: Doug on 12 Feb 2019 at 00:20
Eric,

You only need to take the outer cover off the gearbox to examine and work on the kick start mechanism; you do not need to disturb the rest of the gearbox.

Quite possible a tooth has broken.

Douglas always did have a little bit of a problem with kick start mechanisms. The 3- and 4-speeds of the thirties main flaw seems to be a prevalence to jam, particularly when the kick start gear teeth were just starting to engage. They tried to overcome this by using a modified extended addendum tooth form that resulted in the teeth looking rather pointed. Replacing with conventional pinion can cause a problem in miss-matched tooth forms. Same situation as running a 20 degree pressure angle gear with a 14.5 degree pressure angle. Or if both the pinion and quadrant have been replaced with matching standard gear tooth forms, the tops of the teeth can abut when the quadrant starts to engage, which stops the quadrant gear from going into mesh. Hence the pointy teeth; the quadrant is more likely to fall into the tooth space between. Also I think the first tooth on the quadrant may have been eased back and made more 'pointy' so it too would fall into mesh easier.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 04 Mar 2019 at 12:39
The crankshaft has been worked on and the cone rebuilt. However the machinist checked the other end of the shaft and found it was off by 0.2mm on  the end.
Since the bike was running fine until now except for the un-locked crankshaft, is it an acceptable offset or should he make it run straight? (or straighter as he said he had not yet checked if it was S shaped or just bent...)
Title: Re: Douglas Aero 1937
Post by: Doug on 05 Mar 2019 at 05:38
Eric,

I know it is a long and limber shaft on the timing side and the bushing in the timing cover will force it true, but the total indicator reading ought to be less than that. A run out of 0.2mm is going to cause undue wear on the bushing. You want to aim for 0.08mm or better.

-Doug
Title: Re: Douglas Aero 1937
Post by: Red on 05 Mar 2019 at 09:48
Eric

Do you still have your gearbox apart and if so could you take a photograph of the kick start return spring. I did post a request for help a few weeks back as the new spring I fitted to my Aero did not fully return the kick start lever. I have now established that the new spring I got from club spares is for a 3 speed box and not the 4 speed. Unfortunately they don't hold stcck of any other spring for the Aero and the problem is further complicated by the fact that the club does not have an orginal drawing of the 4 speed spring. Before I or the club get some made I would like to make sure that we know what the correct spring looks like. The broken one I removed from my gearbox again does not appear to be correct and probably why it failed. Photographs of the spring I got from club spares and the broken spring are attached to my original post. Any help will be greatly appreciated.

Roy
Title: Re: Douglas Aero 1937
Post by: Eric S on 05 Mar 2019 at 20:15
Gear Box still closed but springs has been replaced at least twice by previous owners over the last couple of decades. But I will let you know and in any case I will post questions and pictures here.
Title: Re: Douglas Aero 1937
Post by: Red on 06 Mar 2019 at 09:28
Hi Eric

Maybe your bike has also been fitted with the wrong return spring and this is why it has failed a couple of time. If you can provide a photo at sometime it would be very helpful and hopefully we may eventaully be able to get some correct springs made up. Thanks

Roy
Title: Re: Douglas Aero 1937
Post by: Eric S on 17 Mar 2019 at 15:07
Sorry I hadn't yet opened the kick mechanism.
Got the flywheel back from the machine shop.
And of course, waiting for those parts I did not managed to give the tanks a good cleaning and resin treatment and still need to give a coat of paint on the magneto plate.
On this plate we have the oil tap. I removed the screw holding in in place and the mechanism/tap/glass aluminium body do not comes off. Is there any trick there? Any other bolts/screw/nut to remove?
I did not removed and do not plan to remove the oil pump itself.

Also I see on the oil tap a plastic disc numbered 0 to 3 with a needle on top of it that can be rotated like to have an adjustment mark.
I assume the disc must be rotating with 0 matching the ratchet when closed and then the driver can adjust to 1, 2 or 3 with the needle placed to the most common setting for his bike.
I don't remember having seen anything in the manual about that.

There is a bolt holding the tap on the body. Is it just a question of removing the nut to get the tap off?  I assume the tap has a "plug" on the bottom of its shaft. Will it come off the body?
Is there any adjustment on this nut as it looks like if the nut interfere with the tap adjustment.
Title: Re: Douglas Aero 1937
Post by: Doug on 17 Mar 2019 at 16:02
Eric,

There are two screws holding the oil sight glass to the corbel on the timing cover. One is the external screw that you readily see. The second is in the bottom of the bowl, where the oil drains out. You have to remove the glass to access it, but if you clean it up a little, you should see two slots for a screwdriver to facilitate removal.

The numbers on top of the oil flow needle do not correlate to any unit of measure. They are just for reference so that you can return the adjustment to any previous value that you found satisfactory. You would set the pointer to the value that gave the optimal oiling rate for normal riding conditions.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 03 Apr 2019 at 15:42
I am preparing the cylinders and heads after having painted them with a special paint for bike's engine.
1. I should have made it before painting but how do you remove the black carbon residu that we have near the valves and in the head?

2. The surface on the head and cylinder gasket plan is not so nice. I don't plan to have them grinded but I would like to have a good cleaning. Is it a good idea to use a piece of glass (supposed to be flat and I have the old sand cabinet window that has been sanded !) and 800 grid abrasive compound?

3. About grinding the valves seats, I have Abrasive compound in 240 and 800. Which one can I use?

4. I know that I have to anneal the brass/copper head gaskets. What is the best way to do it?

5. I guess I have to clean the inside of the cylinders/barrels. Do we have to use this tool below?
Title: Re: Douglas Aero 1937
Post by: Doug on 12 Apr 2019 at 15:36
Eric,

There are some carburetor cleaners that will soften carbon deposits but it is probably not worth the risk to the new paint. So typically one manually scrapes the carbon off with a copper or aluminum tool that will not cut into the iron.

A plate of flat glass and abrasive compound is the classic way to lap a surface flat. But it is slow and eventually will wear the glass to a non-flat condition. I use a sheet of wet/dry silicon carbide paper (sandpaper) tapped to a flat surface. This saves wear and tear on the flat surface, and one can start off with coarse grit and rapidly change to finer grit. Nowadays it is easier to find a range of different grit sandpaper in one's workshop supplies than a range of grit compounds. Some light oil or soapy water on the paper will stop it from clogging up too quickly.

Valve lapping. I tend to go with what I have on the shelf in the coarse, medium, and fine grits without looking at the numerical grit value. Some of the tins are so old the labels are not legible anyway!

To anneal copper you heat it to a dull red (in dim light) and either allow it to cool in air, or plunge in a bucket of water. I have seen temperatures quoted of anywhere from 400C to 700C. Quenching in water does have the advantage of cleaning the surface. A little acid in the water will help if the discoloration/scaling is tenacious.

The tool shown is typically what is used here to clean and lightly hone brake cylinder bores. I suppose larger versions can also be used to clean cylinder bores and remove cylinder wall glazing and put in a new cross-hatch pattern to help new piston rings to bed in. But I would not expect that type of hone to do much to resize or true up a bore, nor would I use it to remove a cylinder ridge (the ridge formed where the top piston ring stopped.)

-Doug


Title: Re: Douglas Aero 1937
Post by: Eric S on 13 Apr 2019 at 09:53
Thank you Doug

As for the de-glazing of the cylinder's wall, if you don't use a tool, how would you do it?
I am not using any new part (rings or pistons) and I have not seen any cylinder ridge.
Title: Re: Douglas Aero 1937
Post by: Doug on 13 Apr 2019 at 14:59
Eric,

Usually for de-glazing you would use an inexpensive tool such as this:

(https://www.douglasmotorcycles.net/aa-files/images/doug/2019/de-glazing-tool.jpg)

But if you did not want to buy a tool at all, I suppose it could just as well be done with a flexible hand abrasive pad like 3M ScotchBrite or similar nylon matting embedded with silicon carbide grains. Then just get in there with your hand and a helical motion. The cutting action will be so slow that unless you are at it for hours I doubt that you will make any alteration to size or wear any local hollow spots into the cast iron.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 03 Jun 2019 at 18:00
I guess I can say that the re-assembly started, at last.
Lapped and installed the valves.
Any one can confirm the parts are assembled the right way on the valves?
Just noticed that the 2 springs on one cylinder are different than the 2 springs on the other cylinder.
It's barely noticeable on the pictures but the springs are smaller in diameter on 1 half (upper) of their lengths. Any comment?
It's how they were and I put them on the right cylinder. Although I am not sure of the inlet/exhaust position but I lapped them anyway...
Title: Re: Douglas Aero 1937
Post by: Aero on 04 Jun 2019 at 13:48
If it helps my springs are all like the one on the right in your pic. As regards the others with smaller diameter at one end personally I'd fit them with the smaller diameter at the top (collett end). Good luck with the rebuild.
Title: Re: Douglas Aero 1937
Post by: Eric S on 29 Jul 2019 at 10:59
Well I have not worked too much on the Douglas recently. My lack of engine experience makes feels like I am facing a mountain and I am not sure I can make it to the top.

Anyway, I was having a look at the cover that bear the oil pump and dynamo considering painting it.
However I need to remove the oil drip tapet. There is a large nut in the system, under the glass. However the dripping tube is in the way. This tube moves a little bit but stays in place. Can I pull on it to take it off? Is it just slide in?
Title: Re: Douglas Aero 1937
Post by: Aero on 30 Jul 2019 at 15:19
I am not sure if the tube is easily removable, but I did manage to undo that slotted bolt without removing the tube.

If you remove the small bolt at the rear of the oil drip assembly then it is possible to turn the whole assembly anti-clockwise which loosens the slotted bolt & then it can be easily removed with a flat blade screwdriver.

Be careful that you do not lose the tiny spring & ball bearing that resides at the rear of the top assembly, as it will fall out when you turn the assembly.

My spring was broken into 2 pieces, so I wound a new one out of music wire (guitar string!).
Title: Re: Douglas Aero 1937
Post by: Doug on 30 Jul 2019 at 19:23
Eric,

I seem to recall the oil bib threads in, but I was able to work around it in-situ with a screw driver to undo the hollow screw in the well of the bowl.

-Doug
Title: Re: Douglas Aero 1937
Post by: Red on 31 Jul 2019 at 15:30
On my 600 Aero and my son's 500 Aero the drip tubes are screwed in. I used a pair of thin nose pliers just to gently rotate the tube. Refitting the tube is a bit fiddly or my fingers are too big. I inserted the tube into a bit of thin rubber pipe and was then able to screw the tube back in place giving it a final tighten with the pliers.

Roy
Title: Re: Douglas Aero 1937
Post by: Eric S on 09 Sep 2019 at 18:32
I finally went ahead and prepared the parts to put them together.
I am anxious as I never went so far in disassembling an engine and would like to avoid making mistakes in re-assembling.
Plan is
1- install the bearings
2- Close the 2 Halves on the crankshaft.
3- Install the pistons and cylinders
4- Install the timing side
5- install the oil pump side and generator.

And what do you think of my pistons? I have 2 scratches on the side.

Sorry pictures are a bit large :roll:
Title: Re: Douglas Aero 1937
Post by: Aero on 09 Sep 2019 at 19:59
Hi Eric,
the marking on the pistons would suggest to me that there is insufficient piston to bore clearance.
I have had similar issues with my engine & had to hone the bores twice.
It seems these engine need a lot more clearance than most machine shops realise.
At the top of the piston just below where the rings sit you need around 6 to 7 thou clearance, and at the bottom of the skirt you need around 5 thou clearance, piston to cylinder, measured at right angles to the piston pin.

It would also be a good idea to have a trial assembly of the crankshaft, bearings & crankcases, to see if you need to shim between the crank & the bearings to get the crankshaft axial clearance down to a reasonable level.
Mine needed around a millimetre each side, although I have also installed a thin 0.15mm paper gasket between the crankcase halves.
Originally there would have been a 1mm thick oil thrower washer installed on each side of the crankshaft, which would account for the need for shims around the same thickness.
Title: Re: Douglas Aero 1937
Post by: Doug on 10 Sep 2019 at 00:34
Eric,

I am personally not a fan of plastic cages for bearings used in engines. Particularly ones where you often have to heat the case up to drop the bearing in and out. Also, the one on the timing side looks to be very light duty, given the few number of bearing balls.

As mentioned already, you will need to assemble the crankshaft in the cases at least once to test the end float. There are ways to pre-measure this, but most folk do not have the measuring equipment and fixturing to do it. I forget now if the Aero 600 was still this way, but earlier engines were designed for a 21mm wide bearing that even then was becoming obsolete so they incorporated a 1mm shim with a 20mm wide bearing. Even if that was addressed, they still typically bored the flywheel side deep so as to allow for a few shims to get the end-float just right. The shims go between the flywheel side crankcase and the ball bearing.

The pistons look like they have been clawed by a bear! That is more than what would be described as a few scratches... Ease down the high spots and reuse with new rings. It is not ideal, but probably you do not have much choice as pistons are getting hard to come by. Is that recent or old history? If recent, then there is still a problem that will need to be addressed as to why the pistons seized.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 10 Sep 2019 at 08:04
Thank you Doug and Aero
You point out the weak design of the bearing. Maybe I shall use the old one that was not really bad.

As for the pistons, they have no history. I just removed them to work on the crankshaft and have the flywheel cone rebuilt. I just took them off and put them aside.
I didn't had any trouble with the engine as far as I can tell. Only problem was the clutch.
There is no matching seizing marks in the cylinders as far as I can see. Even though the cylinders are not nice. I will send pictures of them later.

Do you have links to get rings?
Title: Re: Douglas Aero 1937
Post by: Eric S on 10 Sep 2019 at 17:59
Here are the pictures of the cylinders. 2 of the same cylinder as it came off the engine. One slightly honed.
Title: Re: Douglas Aero 1937
Post by: Aero on 10 Sep 2019 at 21:06
They look like they need a bit more honing. As mentioned previously check the piston clearances to see how little or much you can hone. For the last 10 seconds of honing, with the drill on slow speed, move the hone rapidly up & down the length of the bore, this will give you a nice "cross-hatch" finish that will help the rings bed in quickly. There is a place near me (Shropshire) called FW Thornton who will supply piston rings worldwide.
Title: Re: Douglas Aero 1937
Post by: Eric S on 11 Sep 2019 at 08:46
Thank you for your help.
I called the mechanic that made the cone and I will visit him on Monday so he can have a professional look and measures of cylinders and pistons. He will check for roundness or lack of the cylinders.
I will have him check this tiny bearing too and the rest of the engine.

In the meantime I would appreciate to get the factory dimensions of the pistons so I can check if I have originals or replacements as well as the bore dimensions.
Title: Re: Douglas Aero 1937
Post by: Eric S on 16 Sep 2019 at 10:54
Anybody could tell me if those pistons are originals?
Anydimesions available?
Title: Re: Douglas Aero 1937
Post by: Aero on 16 Sep 2019 at 19:31
They look like Hepolite replacements, the same as mine.
Standard bore is 74mm, with oversizes at 20, 40, & 60 thousandths of an inch, so roughly 74.5mm, 75mm, & 75.5mm.
If you clean the piston tops the oversize should be marked "20 thou" etc on the crowns, together with Hepolite or Heplex. They are unavailable new these days.
Title: Re: Douglas Aero 1937
Post by: Eric S on 19 Sep 2019 at 08:12
Do we know if Hepolite replacements are the same dimensions everywhere as the originals. We may have to chase for replacements so need to know what we are looking after. If we found replacements that are different than the Hepolite but same as originals it would be too bad to miss them.
Title: Re: Douglas Aero 1937
Post by: Aero on 19 Sep 2019 at 12:40
Original (I assume) on the left, Hepolite on the right
Title: Re: Douglas Aero 1937
Post by: Aero on 19 Sep 2019 at 12:43
Underside
Title: Re: Douglas Aero 1937
Post by: Eric S on 30 Sep 2019 at 10:14
I talked to the engine builder this morning.
Cylinders are measured at 74,75mm. Pistons 74,60mm
Cylinders' walls are porous and he's advising re-boring.
However how can I get new pistons? What are the options? He advised against custom made pistons as quality is not really good on his experience...
Title: Re: Douglas Aero 1937
Post by: eddie on 01 Oct 2019 at 08:29
Eric,
        If the bores are not marked, don't get them rebored - rebuild the engine with the old pistons, but fit new rings. With .15mm clearance, they should be fine! Ignore the comment about reboring because the bores are 'porous' - taking another .25mm cut wont make them any better - in fact, 'porous' bores will retain more oil and prevent further 'nipping up'. Also, don't get too paranoid about the quality of repro pistons - the originals wouldn't have been any better.
    When you rebuild your engine, build it on any cheap motor oil until it is 'run in' - then go over to a better quality oil. Modern oils are so effective that the running in process doesn't get completed before any high spots become glazed. ( I used to work on marine diesels, and one of our craft had to have all the liners and pistons replaced under guarantee because too good an oil had been used during the running in period, and the bores had become glazed!)

  Regards,
                  Eddie.
Title: Re: Douglas Aero 1937
Post by: Eric S on 01 Oct 2019 at 14:59
Great thank you Eddie for bringing some good news.
I assume it still have to be honed though??
Just in case so I/we know, what would be the options should one need pistons?
Title: Re: Douglas Aero 1937
Post by: Aero on 02 Oct 2019 at 11:51
As Eddie has already said, 0.15mm is a good clearance so best to just lightly hone any marks out of your cylinders & re-use the old pistons.
I have a couple of good used pistons measuring 74.7mm if ever you get stuck in the future, but I'm holding on to them for the moment in case I find any spare barrels.
Title: Re: Douglas Aero 1937
Post by: Eric S on 21 Oct 2019 at 19:04
I got the engine parts back.
They surfaced the heads, the top of the cylinders and honed the cylinders somewhat.
As said earlier, he was concerned about the surface quality of the cylinders being porous but I asked him just to hone the cylinders without re-boring them so he did the best he could.
They supplied new rings but did not cut them. He told me to adjust with a 0,4mm/.016" gap. Is that OK?
Title: Re: Douglas Aero 1937
Post by: Aero on 22 Oct 2019 at 18:27
It looks like your engine builder has used long honing stones.
In this instance I think a flex (ball) hone would do a better job.
Somewhere between 12 & 16 thou is ok for the ring gap.
If you gap them now at 12 thou by the time they've bedded in they will probably be more like 16.
Title: Re: Douglas Aero 1937
Post by: Eric S on 04 Nov 2019 at 10:04
Looking at reassembling the engine now and here is a first question.
The bearing on the crankshaft, clutch side is a tight fit and slides in tightly. Surface on the shaft is rough. Removing the burrs may make the bearing loose on the shaft.
How would you do it. Install it with some kind of compound, dry, file off the burrs?

Also I have an oil sling on the same side on top of the bearing. How can I measure and determine if I need any more spacers/washers. How close does it need to be?
Title: Re: Douglas Aero 1937
Post by: Eric S on 11 Nov 2019 at 22:07
No Idea?
Title: Re: Douglas Aero 1937
Post by: Doug on 13 Nov 2019 at 02:20
Eric,

The state of this engine continues to dismay!

I would stone off the burrs. It is a similar situation to the practice of center punch marking shafts. Besides being a deplorable practice, over time the high spots get compressed, resuming the original slack fit. Better to know now if the fit is slack and not providing the proper support and remediate it.

I do not know if this is worth the trouble for a single engine, but I made a simple gauge to measure the end float of the crankshaft for the DT engine since I have done a several and have a few more to do. This is a cylinder of aluminum turned to just a little under the ball bearing outer diameter so that it is a slack fit . Both ends are faced square with a chamfer equal to the bearing radius. The length is not critical other than it needs to be a little less than the distance between the bearing bores. To use, the measuring cylinder is inserted into where the bearings would go and the crankcase bolted up tight with any gaskets that you will be using. The measuring cylinder is push all the way to one side until it bottoms and a dial indicator is arranged to contact the end face and the indicator zeroed. The measuring cylinder is then pushed to the other side until it abuts and the indicator reading of the distance traveled observed. The distance inside the crankcase is the indicator reading plus the length of the cylinder. Then I assemble the bearings and slingers onto the crankshaft and take a measurement across the outside. I then can figure out how much shim is required to achieve the desired end float. That enables me to set the end float in one try. It requires several things not everyone may have available; a bar of metal, an lathe, and measuring equipment.

The traditional way is to assemble the crankshaft into the crankcase and using a mallet, thump the crankshaft to one side and measure the distance from some reference point on the crankshaft relative to a reference point on the crankcase. Then using the mallet to shift the crankshaft to the opposite side the measurement is repeated. That tells you the end float of the crankshaft. You then add or remove shims from behind the bearing races (usually on the flywheel side if both mains are ball bearings) to correct end float. The nuisance is the bearings are a shrink fit in the cases, so you have to go through several sessions of heating the crankcase to pop the bearing in and out as to experiment with shims.

-Doug
Title: Re: Douglas Aero 1937
Post by: Eric S on 14 Nov 2019 at 16:22
Doug

thank you for this information
The thing is the shaft has no really burrs or high spots. It's just not smooth. Bearing slides in and out without feeling any rough surface. It just pops in and out. It's a bit tight and I have to play it around so it can slide in. Making the shaft smooth would have some play...

Not sure to understand though. The bearings are inserted in the case and then shims are between the bearings and the crankshaft. It was this way when I took it apart. But why do you say "you have to go through several sessions of heating the crankcase to pop the bearing in and out as to experiment with shims".
Seems to be the opposite than "behind the bearing races (usually on the flywheel side if both mains are ball bearings)"

Then wouldn't it be easier to fit the bearings first and using the aluminum rod sliding bar method measure the required length of crankshaft+shims?
Those are going to be tiny shims but do we want one on each side to center the crankshaft or is it not important?
Title: Re: Douglas Aero 1937
Post by: Doug on 14 Nov 2019 at 17:15
Eric,

The factory installed the shims between the crankcase and the bearing. There are slingers (in some designs) between the bearing and the crankshaft, but these are not intended to be shims. Presumably Kingswood (and other factories) did this to protect the thin and delicate shims. If they were installed on the crankshaft they would be more prone to damage during assembly. The crankshaft journal has a fillet between it and the throw to avoid a stress riser. If the shim registered on the crankshaft, the hole through would have to be bigger than the journal so that it would clear that fillet. During assembly you would have to be careful the shim rode up that fillet and registered on the flat face, else it might get pinched and not allow the bearing to seat fully. Also they might have figure the crankshaft shuffling back and forth the amount of the running clearance would unduly hammer or at minimum compress pinch the thin shims as the crankshaft flexes, so behind the bearing they are static as well as better protected. It seems to be normal practice, not just with Douglas.

I actually do not remember a slinger(s) on my 1936 Aero, but it has been a while since the engine was assembled and I did not take a photo of the assembled crankshaft that I can refer to. Most designs have a shallow spigot for the slinger to register on, just for the purpose to keep it off the journal radius. I do have a picture of the disassembled crank, and I do not see a spigiot for the rabbet so the must have done without.

Anyway, since the shim is behind the bearing, it has to be installed before the bearing is shrunk into the case. And since the traditional method involves some trial and error, the shim (and bearing) needs to be removed/installed several times until one gets the shim amount correct. I think that also answers why you cannot us the aluminum bar to just gauge the distance between the bearing races once in the crankcases.

One could divide the shims between the timing and flywheel side, but to be honest I cannot recall ever finding shims anywhere but on the flywheel side. The amount is so small, that it is neither enough to throw the rods significantly off center, or enough to correct any misalignment of the conrods. The rods rarely are exactly centered nor is it critical (allowing for the usual no rubbing, turns over freely, etc.) The flywheel side crankcase is easier to heat up to fix the bearing; easy access inside and out for the application of heat. I suppose that is why the shims are installed on that side.

-Doug 

[fix typo. 14Nov19. Doug]
Title: Re: Douglas Aero 1937
Post by: Aero on 14 Nov 2019 at 21:57
I used 2 x 0.3mm shims to get my endfloat correct, in conjunction with 0.25mm thick paper gaskets between the crankcase halves.
Might be a good starting point?
PS that is in conjunction with the 2 oil slingers, which are each 1mm thick
Title: Re: Douglas Aero 1937
Post by: Eric S on 16 Nov 2019 at 13:09
I got a bar of aluminum and will turn a tool next week.
so if I got it well we should have :
Shim - Bearing - oil slinger - crankshaft - oil slinger - bearing - shim (if needed)
I had something "different"
Title: Re: Douglas Aero 1937
Post by: Eric S on 19 Nov 2019 at 17:45
Well the bar I got was too small in diameter so I had to use regular washers lathed down.
I screwed one on one side (not proud of the job there), drilled and thread the other end so I can use an adjusting screw.
Then another washer and a plate of aluminum (I might as well use on this plate) with a small hole to slide a scredriver and I have an adjustable gage that can be measured out of the engine.
Thank you Doug for the idea to use this kind of tool.
When I will have measured this length and that of the crankshaft, I will come back and see what I need in term of shims and oil slingers.
Title: Re: Douglas Aero 1937
Post by: Eric S on 22 Nov 2019 at 07:53
Well the design of my tool may work with somebody with better lathe skills than me. But the play in the screw, the staking of washers makes it 0,3mm "bent" from one side to the other.
Now the question is how accurate do we need to be there? I assume we still need to have a bit of play between the crank and the engine?
Title: Re: Douglas Aero 1937
Post by: Eric S on 27 Nov 2019 at 08:48
Sorry, anybody can help me on my question?
Title: Re: Douglas Aero 1937
Post by: Aero on 27 Nov 2019 at 09:13
I couldn't find any mention of crankshaft end float tolerances anywhere so set mine to 4 thou & the engine is running well.
I also fitted a modern nitrile oil seal to the flywheel side crankcase whilst the engine was apart, as there is enough lube for the primary chain & clutch  from the breather alone on these engines
Title: Re: Douglas Aero 1937
Post by: Aero on 27 Nov 2019 at 13:21
Heres a pic of the seal mod
Title: Re: Douglas Aero 1937
Post by: Eric S on 27 Nov 2019 at 16:56
The engine has the same modification...
Title: Re: Douglas Aero 1937
Post by: Eric S on 29 Nov 2019 at 11:25
So nobody have any advice except Aero on crankshaft end float tolerances? .004" seems tight for me.

Then where will I found the shims? Can we buy them off the shelves?
Title: Re: Douglas Aero 1937
Post by: Aero on 29 Nov 2019 at 14:07
Don't forget you are in effect levering against the end of the crankshaft every time you pull your clutch in.
Too much end float & you will actually see the flywheel move out when the clutch is applied.
Trust me, it is not the first time I have done this ;)
Shims are easily available on ebay.
Title: Re: Douglas Aero 1937
Post by: Eric S on 04 Dec 2019 at 13:09
I managed to make some measures as best as I could. Some parts are not easy to measure s I did my best.
Adding the bearings and the crankshaft, I come to 121.94mm - 122.34mm
The engine blocks as from face to face 124.14-124.44mm

That leaves 1.80 to 1.2mm for the oil slings and shims. I have oil sling (OK did not measured it and it is not smooth, so may replace it?) (That's .071" to .098")
Do I need oil slings on each side? I had one only on the flywheel side.
If I can get oil slings of such a thickness that I don't need shims, am I OK?

Sorry but I have not been able to find shims on Ebay (not familiar at all with this site) and our local machinists have nothing.
Saw a laser cutting company but they have only 1mm 1.2mm and 1.5mm steel. Maybe 2x1mm would fit.
do I need stainless steel or regular steel for shims and oil slings?
Title: Re: Douglas Aero 1937
Post by: Aero on 04 Dec 2019 at 20:37
Are you going to use thin gaskets between the crankcases, as you will need to allow for those too? I used 0.25mm paper.
Heres a link for shims, but there are plenty of others if you search when you know the exact size
https://www.ebay.co.uk/itm/0-5mm-THICK-SHIM-WASHERS-HIGH-QUALITY-STEEL-DIN-988-ALL-SIZES/253287469547?hash=item3af91c11eb:m:mL7tYo9RonYTvbphx9unn2w
Title: Re: Douglas Aero 1937
Post by: Eric S on 05 Dec 2019 at 13:39
Yes paper was installed when I measured.
Thank for the link. When they say M42x52mm, does it means 42mm ID and 52mm OD?
I just need to hear from Doug or Eddie for the play I need to leave. Or I'll go with .004" like you did. However based on the lack of accuracy of m measures, I need to know how tight I need to be. I would have then to have it measured accurately somewhere should I need to be "close" or tight.

Is it better to have 1 shim behind each bearing or is it just not important? I mean better to use 2x0,2mm or 1x0,4mm?
Title: Re: Douglas Aero 1937
Post by: Aero on 05 Dec 2019 at 14:52
Thats correct, M42 would be the ID in mm, and 52mm the OD
Personally I fitted the shims between the crank & the oil slingers. This meant I didn't have to remove the bearings to alter clearances.
Maybe not perfect engineering but it works.
Using this method its easy to assemble with no shims, check the end float & then add/subtract shims.
I did have to profile the inside of the shims to clear the radius on the crank however & I would suggest using a single shim and not "stacking" them if using this method.
Title: Re: Douglas Aero 1937
Post by: Eric S on 05 Dec 2019 at 15:11
Then did the oil slinger act as a shim?
Do you use oil slingers on both sides?
Title: Re: Douglas Aero 1937
Post by: Aero on 05 Dec 2019 at 15:30
The oil slingers were 1mm thick & the diameter was just big enough to obscure the ball bearings.
I used one 1mm slinger & one 0.3mm shim on each side of the crank.
This gave me 4 thou clearance. I was aiming for between 4 thou & 8 thou.


Title: Re: Douglas Aero 1937
Post by: Eric S on 05 Dec 2019 at 18:13
Right now I have 2x1mm 30x52mm oil slingers on the flywheel side.
Bearing "opening" is 52mm so the slinger barely covers the opening. Picture 1

On the link you gave earlier they offer 30x42. So OD is a bit small. Will it work?
The ones from the engine have a rough surface and there is 2. Picture 2
Can I still use them as they are larger or is it better to use a single piece, smooth although smaller?

On the timing side, the bearing is thicker than the shaft it rides so adding an oil slinger would take it off the shaft even more. Picture 3
Is it acceptable?
I can get a 25x35 slinger, with a bearing opening of 47mm !? Is it better than none?

Now inside the timing case, I had a real bad shaped shim/Washer/piece of garbage bent(!) to be roughly 3mm thick. Picture 4
Do I need it? Shaft here is 19mm and I could get a 20x28
How large and how thick I want it??

Now If we can use oil slinger of different thickness, why would one bother with inserting shims behind the bearing(s)? Isn't it more simple to ajust via the slingers?
Which brings me back to the same question, what are the required tolerances as thick shims/washers comes in 0,5mm increments?
Or shoudl I source other more size suited shims and slingers?
Title: Re: Douglas Aero 1937
Post by: Doug on 05 Dec 2019 at 18:33
Eric,

The oil slingers are factored into the design so an not included as part of the shims per se; same as factoring for the width of the bearings. If manufacturing and tolerance were precise enough there would be no need for shims. The factory would just machine to the required dimensions and on assembly it would have the requisite end float. But Kingswood's overall machining accuracy plus the variables of all the individual tolerances on the components of the crankshaft add up to quite a stack of tolerances which result in too much variation. So they make the bearing pocket too deep, and bring the end  float back to the desired limit with shims.

They did not offer various width slingers to serve as a means to adjust end float. Presumably the traditional method of using standard, commercially available shims and popping the bearing in and out posed no difficulty for them. They were use to doing it every workday. They might even had some sort of fixturing or tooling that allowed them to pre-measure and set the shimming so they only had to install the bearing once.

But it is a thought. You might find it easier to make a custom slinger of the desired thickness rather than dealing with the aggravation of removing and installing the ball bearing from the case. I think this would be preferred to using shims between the slinger and the bearing. As already stated, one thick shim is better than multiples of thinner shims. Also, it can be arranged more reliably with the slinger not to get pinched on the radius of the main journal. (While I was typing this, I see you replied with much the same idea.) You could put the shim between the slinger and the bearing (inner race), but this is bad practice from two points. One, the inner race can rotate or creep on the journal, and you want the shim between two static members. Second, it increases the gap between the slinger and the bearing and one of the purposes of the slinger is to keep any larger, stray metal crumbs from getting into the bearing and causing catastrophic failure. Of course the smaller metal particles have probably already trashed the balls and races, but I believe that was the theory!

I have never seen a published figure for the end float on Douglas engines. You were expected to return to the factory or at least the local Douglas Dealer for that sort of repair. So you have to rely on general values from other engines or publications. That timeless source of information "Tuning for Speed" suggests 0.005" for speed work where the crankshaft does not require positive location (such as for the mesh of bevel gears to drive an ohc.) A maximum given as 0.010". Personally I would aim for about 0.004" as already suggested, just to make sure there is some clearance. While the crankshaft does run hotter, the aluminum crankcase will expand more so the clearance will only increase when the engine warm up. In theory you could aim for zero, as the clearance will increase with temperature, but I would not do so. I suspect the crankshafts whip a bit and that might just side load the bearings even more than usual if there was not some clearance to begin with. It also heats up first before the crankcase. I think 0.010" is just a little too much for a road going engine of the period (unless it is a Scott) so would not settle for anything over 0.008". With reliable measuring, I can usually get it within two thou of what I was aiming for (0.004-0.006") without going bonkers over it.

-Doug